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Hot tub water test: what to check before you get in

Updated: 21 October 2026

You are about to get into a hot tub that three people used yesterday, and the bottle by the steps is a pool strip with no bromine scale. A hot tub water test is a before-use habit, not a weekly pool ritual. Warm, small volumes move faster than a garden pool, so sanitiser and pH are the readings you take before you soak. The numbers below come from BISHTA’s factsheets, which do not all use the same chlorine line, so this page keeps them apart. Strip prices are the ones in the [pool tester comparison](/hub/pool-care/pool-tester) on 19 October 2026. We did not lab-test a tub. A qualifying purchase can earn a commission at no extra cost to you.

You are about to get into a hot tub that three people used yesterday, and the bottle by the steps is a pool strip with no bromine scale. A hot tub water test is a before-use habit, not a weekly pool ritual.

Our top picks

Clearwater Clearwater 4-in-1 test strips

Best overall

Clearwater Clearwater 4-in-1 test strips
6.6/10about £9.99
View offer
HOVIRAN HOVIRAN hot tub test strips

Best value

HOVIRAN HOVIRAN hot tub test strips
6.6/10about £7.29
View offer
EASYTEST EASYTEST 3-in-1 test strips

Alternative

EASYTEST EASYTEST 3-in-1 test strips
7.2/10about £11.04
View offer
On this page
  1. 1.Test before you get in
  2. 2.The numbers on the BISHTA sheets
  3. 3.Pads that match the tub you actually run
  4. 4.A tub other people pay to use

Test before you get in

BISHTA’s water-treatment sheet says you test pH and sanitiser before use. If you only dip after a weekend, you are looking at water you have already sat in. Do not trust a pH pad in the first 20 minutes after use. Jets off, sample away from the waterfall, then the strip. The seconds on the bottle stay on how to use pool test strips. Four soaks a week is about 16 dips a month. Clearwater at £9.99 is titled as 50 strips, with one bullet that says 25. HOVIRAN is 125 strips at £7.29. EASYTEST states 90 days once opened, and four dips a week will not finish 150 strips in that window. Buy the count you will use while it is still in date.

The numbers on the BISHTA sheets

Bromine on the water-treatment sheet is 2–4 mg/l. Chlorine on that sheet is 3–5 mg/l. The maintenance sheet says inorganic chlorine 2–4 mg/l and stabilised chlorine 3–5 mg/l. Do not collapse those into one line that says chlorine should be 3–5. pH on these sheets is 7.0–7.6, wider than PWTAG’s managed-pool band of 7.0–7.4. Alkalinity is 80–120 mg/l on the water-treatment sheet and 80–160 ppm on the maintenance sheet. Quote the sheet you are using. PHMB at 50 mg/l is on the BISHTA sheet and is not a pad in this comparison. A fine pad after a shock is not a cleanliness certificate, because chloramines and bromamines can make a sanitiser colour look acceptable when the useful sanitiser is not.
Clearwater Clearwater 4-in-1 test strips

Testsieger

Clearwater Clearwater 4-in-1 test strips
6.6/10about £9.99
View offer

Pads that match the tub you actually run

Clearwater, Canadian Spa, HOVIRAN, both EASYTEST bottles and HLLNWB name bromine. AquaChek yellow at £12.15 does not. Its cyanuric acid pad is the outdoor-pool extra. That case belongs on the pool test kit buying guide. Canadian Spa and RAP put free chlorine and bromine in one description. You read that pad on the chemical you use. You do not add the two scales. HOVIRAN’s uses line names them separately. The title says 3-in-1 and a bullet says seven parameters, then names four tests. Buy the uses line. The Lovibond kit is free chlorine and pH, 20 tests at £19.99, and a bromine scale is not stated. Clearwater at 4.6 from 14,072 is the chart reviewers most often call easy. HLLNWB at £7.99 names bromine, and UK reviews say colours are missing from the chart. A pad list you cannot match is not a spa test.

A tub other people pay to use

A private tub at home is not a commercial spa. BISHTA’s note on HSG282, for spa-pool systems in that scope, says test chlorine or bromine and pH at least twice a day, take a monthly microbiology sample, and test for Legionella quarterly. A strip does not detect Pseudomonas or Legionella. If guests pay and the reading is strange, close the tub and get a proper sample. Do not switch from bromine to chlorine because one pad looked odd. BISHTA says you do not change sanitiser without the retailer, and you do not mix the neat chemicals.

Common questions

How often do I test a tub at home?
Before you use it. BISHTA’s water-treatment sheet says test pH and sanitiser before use. Wait 20 minutes after use before you trust a pH reading. A hired tub is closer to the HSG282 pattern BISHTA summarises: at least twice a day, plus monthly microbiology. A family tub is not that timetable, and it is also not a weekly dip after you have already soaked.
What bromine and chlorine numbers does BISHTA publish?
Bromine is 2–4 mg/l on the water-treatment sheet. Chlorine on that sheet is 3–5 mg/l. The maintenance sheet says inorganic chlorine 2–4 mg/l and stabilised chlorine 3–5 mg/l. Use the line that matches your product. pH is 7.0–7.6. Alkalinity is 80–120 mg/l on the water-treatment sheet and 80–160 ppm on the maintenance sheet. Do not average those into one target.
Can I use pool strips that have no bromine pad?
Only if the tub is on chlorine and the strip names free chlorine or chlorine. AquaChek does not name bromine, so it is a poor match for a bromine tub. Its cyanuric acid pad belongs to an outdoor pool on dichlor or trichlor. A shared free-chlorine/bromine description, as on Canadian Spa, is read on the sanitiser you use. It does not identify which chemical is in the water.
How many strips do I need if I test before every use?
Four soaks a week is about 16 strips a month. A 50-count lasts about three months at that rate, if the pack really contains 50. Clearwater’s title says 50 and one bullet says 25. EASYTEST’s 90-day opened life will not let you finish 150 strips at four dips a week. HOVIRAN’s 125 strips at £7.29 cover a longer run, if you only need the four tests on the uses line.
What if I let the tub to paying guests?
Treat it as closer to a commercial spa. BISHTA’s HSG282 summary says test chlorine or bromine and pH at least twice a day, with monthly microbiology and quarterly Legionella testing. A strip cannot see those organisms. If the colour is odd, stop letting the tub and arrange a laboratory sample. Do not swap in a different bottle and carry on.

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Sources

Public UK sources for managed-pool chemistry, hot-tub factsheets and chlorine colour chemistry, taken from the research digest. Listing prices, stars and review counts are from amazon.co.uk on 19 October 2026.

  1. PWTAG code of practice (retrieved 19 October 2026)
  2. HSE HSG179 — Health and safety in swimming pools (retrieved 19 October 2026)
  3. HSE — swimming pool safety (retrieved 19 October 2026)
  4. PWTAG TN53 — microbiological testing (retrieved 19 October 2026)
  5. BISHTA — water treatment factsheet (retrieved 19 October 2026)
  6. BISHTA — regular maintenance factsheet (retrieved 19 October 2026)
  7. BISHTA — responsibilities for HSG282 for hot tubs (retrieved 19 October 2026)
  8. Camlab — measuring chlorine in a swimming pool or hot tub (retrieved 19 October 2026)
  9. Pool Chemicals — testing guide (retrieved 19 October 2026)