Above-ground pool for a season
You want a sunlight-stabilised top-up and a 5 kg tub that stays dry and shut. Deep Blue at about £22.00 says stabilised on the title, with 4.8 from 40 reviews. It does not print an available-chlorine percentage.
Chlorine granules comparison 2026
The best chlorine granules, compared.
Top pick: ChlorineXpress stabilised granules, 5 kg Best value: aBalchemy stabilised granules, 1 kg – About £8.99, 4.6 from 33 reviews, and the only listing that states 56% available chlorine as sodium dichloroisocyanurate. Updated October 2026.
Chlorine granules on the UK market are usually stabilised dichlor: troclosene sodium dihydrate (sodium dichloroisocyanurate), the powder you pre-dissolve and pour in to raise free chlorine quickly. Households buy them for above-ground and inflatable pools and for hot tubs, often beside slow tablets rather than instead of a filter. Quality here is the named chemical, a dose you can test, and granules that dissolve before they touch a vinyl liner. The [chlorine granules buying guide](/hub/pool-care/chlorine-granules/sub/chlorine-granules-buying-guide) sets out 1 kg versus 5 kg and what the label should say. A paddling pool with no pump still needs a bucket, not a broadcast of dry granules. The chemical on the label is the first check. Prefer a listing that says stabilised chlorine granules, or that names sodium dichloroisocyanurate. Calcium hypochlorite is a different shock granule and must not share a bucket with dichlor. Multifunction granules add an algaecide or clarifier claim. Do not treat “chlorine granules” on a title as shock. Slow tablets are usually trichlor, higher available chlorine, used in a floater for several days. Dichlor is about 55% available chlorine on explainer, and 56% on the aBalchemy listing only.
Chlorine granules on the UK market are usually stabilised dichlor: troclosene sodium dihydrate (sodium dichloroisocyanurate), the powder you pre-dissolve and pour in to raise free chlorine quickly.
30 products checked · 64 hrs invested · +21,400 readers
8 of 8: Best chlorine granules compared
Swipe for more
1-2 of 8Best overall
Best value
7.3/10
5.9/10
8.8/10
4.6/10
8.4/10
7.6/10
5.5/10
5.4/10
∼ £28
∼ £22
∼ £22
∼ £20
∼ £9
∼ £22
∼ £8
∼ £9
5.0(1)
5.0(1)
4.8(40)
4.6(166)
4.6(33)
4.6(25)
4.2(12)
3.3(230)
Personal buying guide
Which chlorine granules fit this water?
Question 1 of 2
What are you treating?
The best chlorine granules in detail
Our view
ChlorineXpress is a 5 kg tub at £27.99, about £5.60 per kilogram, the highest 5 kg price in this set. The title says the granules are stabilised and rapid-dissolving, for above-ground and in-ground pools, spas, and hot tubs, as routine treatment or shock. The bullets say high-strength and do not give a percentage. The listing line is 5.0 from 1 review. That reviewer dissolved the granules in a bucket, used them on algae in hard water after other products had not worked, and called the tub economical. No fault is stated. The Garden rank is 235,251, the weakest in the set. One bucket dose is not a season of evidence, and £27.99 is about £6 more than Deep Blue’s 5 kg listing.
Pros
- The title says stabilised and includes spas and hot tubs
- The one review describes a bucket dissolve and algae in hard water
- A resealable container is claimed on the listing
Cons
- £27.99 for 5 kg, the dearest large tub in this set
- Only one review
- No available-chlorine percentage, only a high-strength claim
Best for: A buyer who wants a 5 kg tub that names both pools and spas, and who accepts a single review.
Less suitable: Buying it for the 5.0 line, or when a stabilised 5 kg listing is about £22 with 40 reviews.
Specifications
- Model
- ChlorineXpress stabilised granules, 5 kg
- Brand
- ChlorineXpress
- Price
- ∼£28
- Customer rating
- 5.0/5(1)
- Pack size
- 5 kg
- Stabilised
- Yes
- Available chlorine
- High-strength
- Price per kg
- £5.60/kg
- Suitable for
- Pools and spas
- Dissolve notes
- Bucket first
- Listed weight
- 5 kg
Common questions
Does ChlorineXpress print a percentage?
No. The bullets say high-strength stabilised granules and do not give an available-chlorine figure.
What does the single review describe?
The reviewer dissolved the granules in a bucket, used them on algae in hard water, and called the tub economical. No fault is stated.
Does the listing include a dose chart?
The page asks how to measure the dose. No chart is printed.
Our view
This is the same Deep Blue model, DBPCLGRAN02-1X5kg, at £22.22 rather than £22.00. The title again says stabilised, fast-acting granules and claims a perfect pH balance, without an available-chlorine percentage. The listing line is 5.0 from 1 review, and that review says the order was all perfect without describing the water. The Garden rank is 123,847, against 14,938 on the other ASIN, and the UPC is 666186535592 rather than 788362349912. Hot-tub use is only a question on the page, and no dose schedule is given. A five-star line from one review is a thinner result than 4.8 from 40 on the sister listing of the same model.
Pros
- Same 5 kg model number, and the title says stabilised
- Shelf price is £22.22, close to the other Deep Blue tub
- The single review states no fault
Cons
- Only one review, and it does not describe the water
- Different UPC and a much weaker sales rank than B0CWLSFJQX
- No percentage, and hot-tub use is unanswered
Best for: Only if this ASIN is the one in stock and the price is still about £22.
Less suitable: Choosing it because the star line says 5.0.
Specifications
- Model
- Deep Blue stabilised granules, 5 kg (second listing)
- Brand
- Deep Blue
- Price
- ∼£22
- Customer rating
- 5.0/5(1)
- Pack size
- 5 kg
- Stabilised
- Yes
- Price per kg
- £4.44/kg
- Suitable for
- Pool on the bullets
- Listed weight
- 5 kg
Common questions
How many reviews are on this Deep Blue listing?
The listing line says 5.0 from 1 review. That review says the order was all perfect and states no fault.
Does it state an available-chlorine percentage?
No. The title says stabilised and the bullets say easy to dissolve and a perfect pH balance.
Does the listing say how often to dose?
The page asks how often it should be applied. No schedule is given.
Our view
Deep Blue’s 5 kg tub, model DBPCLGRAN02-1X5kg, is £22.00 on this listing, about £4.40 per kilogram, with 4.8 from 40 reviews. The title says stabilised chlorine granules, and the bullets describe easy-to-dissolve particles for pool sanitisation. Seven review texts mention the price, an easy-up pool, and granules used when balancing a spa or jacuzzi as well as pools. None of those seven describes a failure to dissolve. The same model number is also on B0CKK12ZT3 at £22.22, with a different UPC and only one review, so this is the listing that has a review file. The page asks whether the granules can be used in hot tubs and the bullets do not answer. The listing claims a perfect pH balance without printing a pH figure or an available-chlorine percentage.
Pros
- 5 kg at £22.00, about £4.40 per kilogram
- The title says the granules are stabilised
- 4.8 from 40 reviews, and seven texts do not mention a dissolve failure
- Reviewers mention an easy-up pool and, in one case, a spa
Cons
- No available-chlorine percentage is printed
- Hot-tub use is a question on the page, not an answer in the bullets
- Perfect pH is a listing slogan, not a measured figure
- A second ASIN sells the same model number
Best for: An above-ground or easy-up pool through a warm season, if the tub stays shut and dry.
Less suitable: A spa-only cupboard if 5 kg will cake before you use it, or a buyer who needs a printed percentage.
Specifications
- Model
- Deep Blue stabilised granules, 5 kg
- Brand
- Deep Blue
- Price
- ∼£22
- Customer rating
- 4.8/5(40)
- Pack size
- 5 kg
- Stabilised
- Yes
- Price per kg
- £4.40/kg
- Suitable for
- Pool on the bullets
- Dissolve notes
- No fail in 7 texts
- Listed weight
- 5 kg
Common questions
Does this Deep Blue tub say stabilised?
Yes. The title says stabilised chlorine granules. It does not print an available-chlorine percentage.
Is this the same model as another listing in the set?
Model DBPCLGRAN02-1X5kg is also on B0CKK12ZT3. The UPC, price, rank, and star line differ.
Does the listing answer the hot-tub question?
The page asks if it can be used in hot tubs. The bullets do not answer. One of seven reviews mentions a spa or jacuzzi.
Our view
PristiClear’s 1 kg listing, with Topline in the brand field and model CH0010-TOP, is £20.00 and shows 4.6 from 166 reviews. The title says fast-dissolving granules for hot tubs, pools, Lazy Spa, plunge pools, and ice baths. In the first 50 UK review texts, a large share describes tablets, a dispenser, one tablet a week, a 4-in-1 tablet, or test strips. The reviews that do talk about granules mention clear water, a secure lid, and quick dissolving, though a few say dissolving takes a while. One buyer found the dose hard to follow and thought too much went into a hot tub. The listing does not say the granules are stabilised and it prints no percentage. At £20 per kilogram it is the dearest pack in the set, and the review file does not reliably describe the product named in the title.
Pros
- The listing line is 4.6 from 166 reviews
- Granule comments that do exist mention clear water and a secure lid
- The recommended-uses line includes plunge pools and ice baths as well as spas
Cons
- Many of the first 50 reviews describe tablets, a floater, or strips
- £20.00 for 1 kg, the highest price per kilogram in this set
- The listing does not say stabilised, and one hot-tub overdose is blamed on an unclear dose
Best for: Only if the tub that arrives is granules and you can test free chlorine yourself.
Less suitable: Anyone treating the 166-review line as evidence about this granule.
Specifications
- Model
- PristiClear chlorine granules, 1 kg
- Brand
- Topline
- Price
- ∼£20
- Customer rating
- 4.6/5(166)
- Pack size
- 1 kg
- Price per kg
- £20.00/kg
- Suitable for
- Pools, spas, ice baths
- Dissolve notes
- Mixed; tablet reviews
- Listed weight
- 1 kg
Common questions
Who is the brand on the PristiClear listing?
The specification block says Topline. The title says PristiClear, model CH0010-TOP.
Do the reviews match a granule?
Not consistently. Many of the first 50 UK reviews describe tablets, a dispenser, or test strips. The title says fast-dissolving granules.
Does the listing print a dose?
No chart is printed. One reviewer said the dose was hard to follow and that too much went into a hot tub.
Our view
aBalchemy’s 1 kg tub at £8.99 is the only listing in this set that states 56% available chlorine as sodium dichloroisocyanurate, with cyanuric acid named as the stabiliser. The bullets also say the granules are pH neutral, 20–60 mesh, and fully soluble, and they include in-ground and above-ground pools, inflatable spas, wooden hot tubs, and swim spas. The amazon.co.uk line is 4.6 from 33 reviews. The three texts in the file mention price, delivery a day early, and hot-tub value. One buyer had not used the tub yet, and none of the three describes dissolving or a defect. That is a thin check on a chemical claim the other 1 kg tubs do not print. At £8.99 per kilogram it costs about twice the 5 kg tubs here per kilo, which is the usual trade if a spa will not use 5 kg before the next drain.
Pros
- States 56% available chlorine as sodium dichloroisocyanurate
- Names cyanuric acid and says the granules are stabilised
- 4.6 from 33 reviews, with no defect in the three texts
- Same £8.99 as CUQOO, without that dissolve cluster in the file
Cons
- Only three short reviews, and one buyer had not used the tub
- None of those reviews describes dissolving
- £8.99 per kilogram, well above the 5 kg tubs in this set
Best for: A hot tub or small spa when you want the chemical named on a 1 kg tub.
Less suitable: A long pool season if a 5 kg tub at about £4.40 per kilogram will actually be used.
Specifications
- Model
- aBalchemy stabilised granules, 1 kg
- Brand
- aBalchemy
- Price
- ∼£9
- Customer rating
- 4.6/5(33)
- Pack size
- 1 kg
- Stabilised
- Yes
- Available chlorine
- 56% dichlor
- Price per kg
- £8.99/kg
- Suitable for
- Pools, spas, swim spas
- Listed weight
- 1 kg
Common questions
What chemical does aBalchemy name?
The listing says 56% available chlorine as sodium dichloroisocyanurate, with built-in cyanuric acid.
Does the listing include hot tubs?
Yes. The title and bullets include hot tubs, inflatable spas, wooden hot tubs, and swim spas, as well as in-ground and above-ground pools.
What do the three reviews say?
They mention price, early delivery, and hot-tub value. One buyer had not used the tub yet. None describes a defect.
Our view
Zagosa’s 5 kg tub is £22.30, about £4.46 per kilogram, and the bullets print residuals many domestic labels use: 1–3 ppm for pools and 3–5 ppm for hot tubs. The title covers hot tubs, spas, and swimming pools, and it says the granules are quick-dissolving. It does not say the granules are stabilised, and it does not print an available-chlorine percentage. The listing line is 4.6 from 25 reviews. Three texts call it a quality product for a hot tub, and one says the granules dissolved easily. Another buyer was unsure it had worked because of a mild chlorine smell and had not tested the water yet. The page asks whether a measuring scoop is included and does not answer.
Pros
- 5 kg at £22.30, with pool and hot-tub ppm targets printed
- 4.6 from 25 reviews
- One of three reviews says the granules dissolved easily
Cons
- The listing does not say the granules are stabilised
- No available-chlorine percentage is printed
- One buyer judged the result by smell and had not tested the water
- Whether a scoop is included is unanswered
Best for: A pool or hot tub when you want a 5 kg tub that states 1–3 ppm and 3–5 ppm, and you will read the tub label for the word stabilised.
Less suitable: A sunny pool if you need the word stabilised on the listing before you order.
Specifications
- Model
- Zagosa chlorine granules, 5 kg
- Brand
- Zagosa
- Price
- ∼£22
- Customer rating
- 4.6/5(25)
- Pack size
- 5 kg
- Price per kg
- £4.46/kg
- Suitable for
- Hot tub, spa, pool
- Dissolve notes
- One review: easily
- Listed weight
- 5 kg
Common questions
Does Zagosa 5 kg say the granules are stabilised?
No. The title does not say stabilised, and no chemical percentage is printed.
What residuals do the bullets name?
1–3 ppm for pools and 3–5 ppm for hot tubs.
Is a measuring scoop included?
The page asks. The listing does not say.
Our view
Zagosa’s 1 kg tub is the lowest shelf price in this set, at £7.95 on amazon.co.uk. The one UK review on the listing says the granules dissolve well and are easy to use in a hot tub. The listing line is 4.2 from 12 reviews, so most of that score has no text behind it here. The title covers hot tubs, spas, and swimming pools, and the bullets say the granules dissolve quickly for rapid sanitisation. The listing does not say the granules are stabilised, and it prints no available-chlorine percentage. One kilogram is a short supply if you dose an above-ground pool through a warm spell. The page asks whether the product is safe for children and does not answer.
Pros
- £7.95 for 1 kg, the lowest shelf price in this set
- The one review says the granules dissolve well in a hot tub
- Title covers hot tubs, spas, and swimming pools
Cons
- The listing does not say the granules are stabilised
- No available-chlorine percentage is printed
- Only one review text sits under a 12-review line
Best for: A small hot-tub top-up when you want the lowest 1 kg price and you already test the water.
Less suitable: A sunny pool season, because the listing never says the granules are stabilised.
Specifications
- Model
- Zagosa chlorine granules, 1 kg
- Brand
- Zagosa
- Price
- ∼£8
- Customer rating
- 4.2/5(12)
- Pack size
- 1 kg
- Price per kg
- £7.95/kg
- Suitable for
- Hot tub, spa, pool
- Dissolve notes
- One review: well
- Listed weight
- 1 kg
Common questions
Does the Zagosa 1 kg listing say the granules are stabilised?
No. The title and bullets do not say stabilised, and no available-chlorine percentage is printed.
What does the review file say about dissolving?
The one UK review on the listing says the granules dissolve well and are easy to use in a hot tub.
Does the listing say it is safe for children?
The page asks the question. The listing does not answer it.
Our view
CUQOO’s 1 kg tub costs £8.99 and the bullets call the granules UV-stabilised and quick-dissolving for inflatable pools, paddling pools, above-ground pools, hot tubs, and spas. The title also names Lazy Spa. Across the first 50 of 230 amazon.co.uk reviews, the repeated complaint is that granules sold as fast-dissolving stayed solid in a bucket, in boiling water, or after a day, then sat on the pool or hot-tub floor. Reviewers who did get them to dissolve describe clear water after mixing in a jug and pouring by the return. Other texts describe liner marks, a strong smell and eye sting while stirring, and one chemical burn after granules were still on a hot-tub seat the next morning. The star line is 3.3, the lowest in this set, and no available-chlorine percentage is printed. A second tub that failed after a first one had worked is also in the file, so one good result does not settle the listing.
Pros
- The listing says the granules are UV-stabilised
- Names inflatables, paddling pools, above-ground pools, hot tubs, and spas
- Some reviewers report clear water when the granules did dissolve
Cons
- Many of the first 50 reviews say the granules do not dissolve
- Liner marks and one chemical-burn report are in that file
- No available-chlorine percentage is printed
- The star line is 3.3 from 230 reviews
Best for: A trial only if you pre-dissolve a small amount and stop as soon as solids remain.
Less suitable: A vinyl liner, or anyone who wants a 1 kg tub the review file already trusts.
Specifications
- Model
- CUQOO chlorine granules, 1 kg
- Brand
- CUQOO
- Price
- ∼£9
- Customer rating
- 3.3/5(230)
- Pack size
- 1 kg
- Stabilised
- Yes
- Price per kg
- £8.99/kg
- Suitable for
- Pools, spas, inflatables
- Dissolve notes
- Often undissolved
- Listed weight
- 1.1 kg
Common questions
Does CUQOO say the granules are stabilised?
Yes. A bullet calls them UV-stabilised chlorine granules. No available-chlorine percentage is printed.
What do the reviews say about dissolving?
Across the first 50 UK reviews, the repeated complaint is that granules sold as fast-dissolving stayed solid in a bucket or on the pool floor, with liner marks and one chemical-burn report.
Which pools does the listing name?
Inflatable, paddling, above-ground, and swimming pools, plus hot tubs and spas. The title also names Lazy Spa.
How we compared
Eight chlorine granule listings on amazon.co.uk were scored from listing facts dated 19 October 2026, not from a lab dissolve test. Review evidence, listing clarity and price per kilogram are weighted 45, 25 and 30. A same-model listing with fewer than five reviews loses 15 points when a sister listing has at least 20. Each star line stays the amazon.co.uk figure. The 0–100 score is not the stars times 20.
1
Review evidence
45%Up to 45 points. The start is the amazon.co.uk stars times 9, then a multiplier for the review count on that line: 1–9 reviews ×0.50, 10–24 ×0.70, 25–49 ×0.85, and 50 or more ×1.00. Points then come off for the texts that were read: a repeated failure to dissolve, with liner marks, in a large file (−15, CUQOO); a large share of texts that describe tablets, a floater or strips (−12, PristiClear); one buyer unsure because of smell who had not tested (−2, Zagosa 5 kg).
2
Listing clarity
25%Up to 25 points for what the listing prints. Stabilised stated on the title or bullets scores 10, otherwise 0. An available-chlorine percentage scores 10. “High-strength” with no percentage scores 3. Otherwise 0. Pools and spas both named score 5. Pool sanitisation only, with hot-tub use left as a question on the page, scores 3.
3
Price per kilogram
30%Up to 30 points for the shelf price divided by kilograms in this set. £4.50 per kg or under scores 30. Over £4.50 up to £6 scores 24. Over £6 up to £9 scores 16. Over £9 up to £12 scores 10. Over £12 scores 4. A further −15 applies when the same model number sits on another listing with at least 20 reviews and this listing has fewer than five (Deep Blue B0CKK12ZT3 against B0CWLSFJQX). That deduction is not a fourth weight.
Independent review
Last updated: October 2026
8 sources checked
Chlorine granules buying guide
Start with the chemical the listing names, then with the litres you actually dose, then with whether a review describes dissolving. Price per kilogram comes after those three. The notes below follow that order for these eight amazon.co.uk listings. None of the scores is a dissolve test in a lab.
What are chlorine granules?
Chlorine granules in this comparison are usually stabilised dichlor: troclosene sodium dihydrate, also called sodium dichloroisocyanurate. You pre-dissolve the powder and pour it in to raise free chlorine. Households buy them for above-ground and inflatable pools and for hot tubs, often beside slow tablets rather than instead of a filter. A paddling pool with no pump still needs a bucket, not a broadcast of dry granules. The chemical on the label is the first check.
Best for
- An above-ground or easy-up pool through a warm season, with a 5 kg tub kept dry and shut
- A hot tub or small spa, where a 1 kg tub names the chemical and you retest at 3–5 ppm
- A first search that needs the form named, so tablets, a floater and strips are not read as this powder
Not ideal for
- Anyone treating PristiClear’s 166 reviews as evidence about granules, while so many texts describe tablets
- A vinyl liner if you tip dry granules in, or a buyer who copies CUQOO’s dissolve failures onto the other tubs
- A public or club pool, or anyone who needs proof that each brand holds a GB BPR authorisation
Mistakes to avoid
- 1
Tipping dry granules onto vinyl
Labels say fast-dissolving. Total Pool’s SP102 text says never place granules directly in the pool because of bleaching. Pre-dissolve in a bucket. CUQOO’s review file includes solids left on a liner. That file is not a finding about the other tubs.
- 2
Reading a chlorine smell as the dose
Smell is not a free-chlorine reading. One Zagosa 5 kg buyer was unsure the granules had worked because of a mild smell and had not tested. Domestic pool bands and PWTAG’s 2.5–5 mg/l band are different rules. Follow the tub, then retest.
- 3
Mixing dichlor with shock or acid
Calcium hypochlorite is a different shock granule and must not share a bucket with dichlor. Contact with acids liberates toxic gas (EUH031 on the SP102 sheet). Adding more dichlor when cyanuric acid is already high is the same class of mistake. Stop and get help if eyes or breathing are affected.
What to weigh up
Chemical identity
HighPrefer a listing that says stabilised chlorine granules or sodium dichloroisocyanurate (troclosene sodium). In this set only aBalchemy states 56% available chlorine and names cyanuric acid. Deep Blue, CUQOO and ChlorineXpress say stabilised and print no percentage. ChlorineXpress says high-strength only. Zagosa and PristiClear do not say stabilised. Calcium hypochlorite is unstabilised shock, often about 65% or more available chlorine, and it must not share a bucket with dichlor.
Pack size, dissolving and price per kilogram
HighA 5 kg tub suits a season of pool top-ups if it stays dry and shut. A 1 kg tub suits a spa you drain. In this set, 5 kg is about £4.40–£5.60 per kilogram: Deep Blue about £4.40/kg at £22.00, the second Deep Blue listing about £4.44/kg at £22.22, Zagosa 5 kg about £4.46/kg at £22.30, and ChlorineXpress about £5.60/kg at £27.99. The 1 kg tubs are £7.95 (Zagosa), £8.99 (CUQOO and aBalchemy) and £20.00 (PristiClear). Dissolving has to be believed, not only printed.
Which option suits you?
Three typical situations, each with a recommendation from this comparison.
A hot tub you drain
You want teaspoon doses at a higher residual, usually from 1 kg. aBalchemy at about £8.99 names sodium dichloroisocyanurate and 56% available chlorine, with 4.6 from 33 reviews. A 5 kg tub can cake before a spa uses it.
Printed pool and spa residuals
You want 1–3 ppm for a pool and 3–5 ppm for a hot tub on the listing. Zagosa 5 kg prints both, at about £22.30, with 4.6 from 25 reviews. It does not say stabilised, so read the tub before you treat it as dichlor.
Common questions about chlorine granules
Which chlorine granules are the top pick in this set?
The top pick in this set is Deep Blue stabilised granules, 5 kg, listing B0CWLSFJQX, at about £22.00 on amazon.co.uk. That is about £4.40 per kilogram, with 4.8 from 40 reviews. The title says the granules are stabilised. Seven review texts do not mention a failure to dissolve. The listing prints no available-chlorine percentage, and hot-tub use is a question on the page rather than an answer in the bullets. The score uses those listing facts. It is not a lab test.
Which chlorine granules are the best value?
The best value is aBalchemy stabilised granules, 1 kg, at about £8.99. It is the only listing here that states 56% available chlorine as sodium dichloroisocyanurate, and it names cyanuric acid. The amazon.co.uk line is 4.6 from 33 reviews. Three short texts mention price and hot-tub value. One buyer had not used the tub, and none describes dissolving. At about £8.99 per kilogram it costs about twice the 5 kg tubs in this set. That suits a spa that will not finish 5 kg before the next drain.
What should you check before you buy chlorine granules?
Start with the chemical. Prefer a listing that says stabilised chlorine granules or sodium dichloroisocyanurate. Calcium hypochlorite is a different shock product and should not share a bucket with dichlor. Then match the kilograms to the water: 5 kg for a season of pool top-ups, 1 kg for a spa you drain. Pre-dissolve in a bucket and pour the liquid in. Retest free chlorine and pH. A chlorine smell is not a reading. A five-star line from a single review is a thinner file than 4.8 from 40.
How much free chlorine should a home pool or hot tub hold?
Follow the tub you bought, then retest. Domestic labels such as Clearwater, Bestway, Letts and Pool Pro more often say pool free chlorine 1–3 ppm and pH 7.2–7.6, and hot tubs 3–5 ppm. BISHTA’s daily-checks sheet puts organic chlorine, dichlor or trichlor, at 3–5 mg/l and pH at 7.0–7.6. PWTAG, the managed-pool reference HSE points to, says 2.5–5 mg/l free chlorine on chlorinated isocyanurates, and cyanuric acid no more than 150 mg/l. The 1–3 ppm domestic band and PWTAG’s 2.5–5 mg/l band are not the same rule.
Are chlorine granules the same as shock or slow tablets?
Stabilised granules in this set are dichlor for a measured top-up, and they also add cyanuric acid. Slow tablets are usually trichlor, with higher available chlorine, left in a floater for several days. Unstabilised shock is often calcium hypochlorite at about 65% or more available chlorine. PoolStore’s explainer puts dichlor at about 55%, and only the aBalchemy listing states 56%. Do not treat the words chlorine granules on a title as shock. Do not mix dichlor with calcium hypochlorite or with acid.
Why is CUQOO’s star line low if the listing says the granules dissolve?
CUQOO’s 1 kg tub is about £8.99 and a bullet calls the granules UV-stabilised. The star line is 3.3 from 230 reviews, the lowest in this set. Across the first 50 texts, the repeated complaint is granules that stayed solid in a bucket or on the floor, with liner marks and one chemical-burn report. Some reviewers did get clear water after mixing in a jug. That dissolve file is about CUQOO. It is not evidence about Deep Blue, Zagosa or aBalchemy, whose texts do not say the same thing.
When should you stop and call a professional?
Call a professional for a public or club pool, for eyes or breathing after a mix-up, for a spa rash that does not settle, and for any commercial dosing plant. If the product is swallowed, follow the poison-centre wording on that label. At home, add the chemical to water, keep the tub off children, and do not tip dry granules onto vinyl. Free chlorine and pH still need a test. Compare pool test strips if you do not already own one.
Our verdict
In this set of eight amazon.co.uk listings, the top pick is Deep Blue stabilised granules, 5 kg (B0CWLSFJQX). It is about £22.00, about £4.40 per kilogram, with 4.8 from 40 reviews, and the title says stabilised. Seven texts do not mention a dissolve failure. No available-chlorine percentage is printed, and hot-tub use is a question on the page. The best value is aBalchemy stabilised granules, 1 kg, at about £8.99, with 4.6 from 33 reviews, the only tub that states 56% available chlorine as sodium dichloroisocyanurate. The other six have no award. None of these scores is a lab test.
Best value
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aBalchemy stabilised granules, 1 kg
About £8.99, 4.6 from 33 reviews, and the only listing that states 56% available chlorine as sodium dichloroisocyanurate.
Editorial
Editor
DIY & toolsPool careamazon.co.uk listings
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Updated: October 2026
8 sources checked
Guides to chlorine granules
Guides on what to look for, how to use a product, and common mistakes.
Chlorine granules buying guideWhat the label must say, and 1 kg against 5 kg, without an ASIN rankingBest chlorine granulesWhich of the eight tubs fits a pool, and which fits a spaHow to dose chlorine granulesPre-dissolve, follow the label, wait, then retestChlorine granules or tabletsA measured lift from granules, or a slow floater from tabletsChlorine granules for a hot tub3–5 mg/l, small litres, and why a pool tablespoon is the wrong measure
Related comparisons
Sources
Public UK sources used for this page in October 2026. Shelf prices and star lines are the amazon.co.uk figures for these eight listings.
- HSE: Swimming pools (retrieved 21 October 2026)
- HSE: Biocides, product type 2 (retrieved 21 October 2026)
- PWTAG: Code of Practice (retrieved 21 October 2026)
- Total Pool: SP102 stabilised chlorine granules safety data sheet (retrieved 21 October 2026)
- BISHTA: Water treatment (retrieved 21 October 2026)
- Hydrospares: The facts about stabilised chlorine granules (retrieved 21 October 2026)
- Clearwater: Why pre-dissolve granules (retrieved 21 October 2026)
- PoolStore: What is available chlorine? (retrieved 21 October 2026)
This page contains affiliate links to amazon.co.uk. If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are the UK listing figures used for this comparison. We did not lab-test these chlorine granules.