The best water softening systems, compared.
Top pick: iSpring WCS15KG Best value: AquaHouse 9 litre – £399.99 salt softener, 583 mm tall, with WRAS number 260502718 printed and not re-checked. Updated 17.10.2026.
Hard water leaves limescale on kettles, showers, cylinders and boilers, and soap lathers poorly. A salt softener swaps calcium and magnesium for sodium on a resin, then regenerates that resin to drain. Four use ion exchange: the BWT WS355, both AquaHouse models and the iSpring. A plumbed softener still needs a cold feed, a drain, a cupboard that fits, and one hard kitchen tap for drinking and infant formula. The [water softening systems buying guide](/hub/hot-water/water-softening-systems/sub/water-softening-systems-buying-guide) sets the stop-rules for type and size. Eddy and Water-King are electronic conditioners sold on the same search. The Drinking Water Inspectorate says this class does not soften.
Hard water leaves limescale on kettles, showers, cylinders and boilers, and soap lathers poorly. A salt softener swaps calcium and magnesium for sodium on a resin, then regenerates that resin to drain.
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Personal buying guide
Question 1 of 2
What should the unit do?
The iSpring WCS15KG is listed at £253.99 as a cold-water ion-exchange softener, with 4.8 from 10 ratings and no review text in the extract. It claims 3/4 inch BSP and 15 gallons per minute. There is no WRAS line, no warranty line, and the 18 × 10 × 5 cm dimension conflicts with the 22.7 kg weight. Capacity is given as 9 litres, with resin described as pre-filled, and the model field says ED2000 against the WCS15KG title. A salt-shortage reminder is claimed, and salt is not listed in the box. Four point eight from 10 silent ratings does not outrank 4.4 from 98.
Pros
Cons
Best for: A buyer who wants a cold-water ion-exchange unit at this shelf price and will check fittings approval separately.
Less suitable: Anyone who needs a WRAS number on the listing, or dimensions they can trust without measuring the delivered unit.
Specifications
Common questions
Is the iSpring WCS15KG a salt softener?
The listing says ion exchange, with automatic backwash and regeneration, for cold water only.
Does the extract state WRAS approval?
No WRAS number is printed.
What size does the listing give?
Capacity is 9 litres and weight is 22.7 kg. The dimension line says 18 × 10 × 5 cm, which the extract does not reconcile with that weight.
The AquaHouse 9 litre is a metered ion-exchange softener at £399.99 with 4.6 from 10 ratings. The title says 1–5 person households. It prints WRAS number 260502718, a 3/4 inch BSP connection and a 2-year warranty. Salt and flexi hoses are extra. The seven UK reviews are mostly short and positive, and one says it is too soon to judge. Allow another 50–60 mm of depth if you add flexi hoses. It is the best value salt unit in this set because a WRAS number is printed and the cupboard height is 583 mm. The number was not re-checked on the live directory, and there is no flow rate on the spec table.
Pros
Cons
Best for: A smaller hard-water household that wants a salt softener around 583 mm tall and will buy salt and hoses separately.
Less suitable: A 5–10 person claim, which is the 21 litre listing, or a no-salt conditioner.
Specifications
Common questions
Does the AquaHouse 9 litre include salt?
No. The listing says salt is not included, and flexi hoses are not included.
What pipe size does it use?
3/4 inch BSP (22 mm) male, with an integrated bypass and a 2 m drain hose. Allow another 50–60 mm of depth if you add flexi hoses.
Is a WRAS number printed?
The listing prints approval number 260502718. This extract does not re-check the live WRAS directory.
The BWT WS355 is an ion-exchange softener listed at £599 with 4.4 from 98 amazon.co.uk ratings. The bullets claim WRAS approval and BS 6920, tablet salt, up to 6 people, and 30 litres per minute. UK reviews praise soft water and quiet running, and they also report a failed screen, extra waste pipes, repeat engineer visits, and one leak quoted at £120 after the labour warranty. The printed warranty is five years parts and two years labour, subject to the conditions on the listing. Pipe size is not in the spec table, and the TDS line says 2400 ppm with no method. It is the top pick here for a hard-water household that wants the ions removed and can fit a unit about 602 mm tall with two waste connections.
Pros
Cons
Best for: A hard-water household of up to 6 people, on the listing's wording, that wants ion exchange and can fit a unit about 602 mm tall with two waste connections.
Less suitable: Anyone who needs a printed WRAS number in the extract, or a no-salt clamp-on unit.
Specifications
Common questions
What salt does the BWT WS355 listing specify?
The bullets say tablet salt.
What did UK reviews say about fitting it?
Reviews mention a regen discharge and a separate overflow, and cutting a cupboard base so the unit sits on the floor. The listing height is just over 600 mm.
What warranty is printed?
Five years parts and two years labour, subject to the conditions on the listing, plus a claim that home commissioning is included.
The Eddy ED6002P-UK is an electronic descaler at £139 with 4.1 from 452 ratings. The title calls it a water-softener alternative, and the bullets say hardness is unchanged, there is no salt and no wastewater. UK reviews are split between less crust and no clear change, including one review at a stated 290 ppm. There is no WRAS number in the extract. The spec table's carbon and ultraviolet line conflicts with the bullets. The listing claims 100 litres per minute, and pipes over 25 mm need extra cable. A plumber-not-required line is the listing's claim, not an Inspectorate instruction. The 452 reviews do not make this the top softener.
Pros
Cons
Best for: A household that wants a no-salt coil unit and accepts the listing's statement that hardness is not removed.
Less suitable: Anyone who needs ion exchange, a WRAS number in the extract, or a guarantee that kettle scale will stop.
Specifications
Common questions
Does the Eddy listing say it removes hardness?
No. The bullets say it does not change hardness, uses no salt, and does not waste water. The spec table also says activated carbon and ultraviolet, which the bullets do not support.
How is it fitted, according to the listing?
Coils on copper, plastic, iron or steel pipe. Extra-length cable is mentioned above 25 mm. The bullets say a plumber is not required. That is the listing's claim.
What did the UK reviews disagree about?
Many describe less crust or a powdery residue. Others say the kettle still furred, or that they saw little change, including one review at a stated 290 ppm.
The AquaHouse 21 litre is a metered ion-exchange softener at £649.99. The title says 5–10 people and light commercial use. It is 1,047 mm tall, uses 1 inch BSP, and prints the same WRAS number as the 9 litre model, 260502718, which this extract does not re-check. The extract has no star line and no review text. The part-number field says AH-WS10L while the model line says AH-WS21L. Salt and flexi hoses are not included. Allow another 50–60 mm if you add hoses. It is the largest resin volume here, and it is a poor fit for a 600 mm base unit.
Pros
Cons
Best for: A larger household that has a tall cupboard and a 1 inch cold feed, and that accepts a listing with no UK review text.
Less suitable: A standard 600 mm base unit, or a buyer who wants review text before paying £649.99.
Specifications
Common questions
Who is the AquaHouse 21 litre listed for?
The title says 5–10 person households and light commercial use, with 21 litres of capacity.
How tall is it?
1047 mm, plus 50–60 mm if you add flexi hoses. Those hoses are not included, and neither is salt.
Are there reviews in the extract?
No star line and no review text. The part-number field says AH-WS10L while the model line says AH-WS21L.
The Water-King WK1-E is listed at £270 as an electronic softener and descaler, with four aerials and a transformer and no star line in the extract. The bullets say no salt, pipes up to 42 mm, and that it softens hot water. There is no WRAS number. The spec field says countertop, which conflicts with the pipe description. The extract does not describe ion exchange. The soften line is the listing's wording, and it conflicts with the Inspectorate statement that this class does not soften. Weight is 750 g, and a 5-year warranty is claimed beside a 25-year design-life line.
Pros
Cons
Best for: A buyer comparing no-salt electronic units for pipes up to the stated 42 mm, who will not treat the soften line as an official finding.
Less suitable: Anyone who wants ion exchange, a WRAS number, or UK review text in this extract.
Specifications
Common questions
Is the Water-King WK1-E an ion-exchange softener?
The extract does not describe ion exchange. It describes electronic conditioning with no salt. The bullets also say it is proven to soften hot water.
What is in the box?
Four aerials and a transformer. The weight is 750 g. No WRAS number is printed.
Is there a star rating in the extract?
No. The installation-type field says countertop, while the bullets describe pipes up to 42 mm.
We compared six amazon.co.uk listings: four ion-exchange softeners and two electronic conditioners. Prices and stars are from extracts dated 15 October 2026. Public checks are the Drinking Water Inspectorate, the NHS and the WRAS directory section named below. There was no laboratory test, no house survey, and no live re-check of printed approval numbers. The weights follow the buying order in the digest. A conflicting dimension, a missing star line, or a soften claim the Inspectorate contradicts is recorded on the product, not turned into a lab score.
Chemistry
25%Whether the listing is ion exchange, which removes hardness ions, or an electronic conditioner, which the Inspectorate says does not soften.
Fittings evidence
20%Whether a WRAS line or a number is printed, and that a printed number was not re-checked on the live directory.
Size and household
20%Resin volume in litres, the stated person count, and whether the height will fit a cupboard. Resin litres are not litres of water a day.
Install path
15%Cold feed, brine drain, bypass, socket and one hard drinking tap for a salt unit, against a coil or aerial claim on a conditioner.
Reviews
12%amazon.co.uk stars and review count. A large count on a conditioner is not treated as removed hardness.
Shelf price
8%The captured amazon.co.uk price. It is not an installed price, and salt or hoses may be extra.
A water softening system on this page is either a salt softener or an electronic conditioner, and those are not the same purchase. Ion exchange removes calcium and magnesium. A conditioner leaves them in the water. Read the hardness from your water company before you compare cupboard heights. The shelf prices below are amazon.co.uk extracts, not installed prices.
A domestic ion-exchange softener swaps calcium and magnesium for sodium on a resin. Salt brine then regenerates that resin, and the brine goes to waste. That is what removes the hardness ions. In this set the salt units are the iSpring WCS15KG, the AquaHouse 9 litre, the AquaHouse 21 litre and the BWT WS355. Eddy and Water-King are electronic conditioners sold on the same search. The Drinking Water Inspectorate says this class does not soften. The Eddy bullets say hardness is unchanged.
Eddy has 4.1 from 452 reviews, and the bullets say hardness is unchanged. The Inspectorate says electronic units do not soften. A large review count does not close that gap.
Ion exchange adds sodium. Keep one hard tap for drinking and cooking. The NHS says not to make infant formula with artificially softened water.
The iSpring dimension line says 18 × 10 × 5 cm beside a weight of 22.7 kg. The AquaHouse price does not include salt or flexi hoses. Measure the cupboard, and do not use an Amazon TDS figure as your hardness.
Chemistry is the first split. Ion exchange removes calcium and magnesium and replaces them with sodium. Salt brine regenerates the resin and that brine goes to waste. In this set that is the iSpring WCS15KG, the AquaHouse 9 litre, the AquaHouse 21 litre and the BWT WS355. A no-salt conditioner leaves the hardness ions in the water. Eddy and Water-King are that second type. The Drinking Water Inspectorate says electronic units do not soften.
A plumbed salt softener needs a cold feed, a brine drain, a bypass, a socket, and one kitchen tap left on hard water. The Inspectorate says use a qualified plumber. Call one for a rising-main tee, backflow doubt, or pipework before a boiler or an unvented cylinder. A DIY line on a clamp-on box is only a listing claim. WRAS section 2450 covers salt softeners on cold water only. An approval expires and is not a performance prize. AquaHouse prints number 260502718 on both listings.
Three typical situations, each with a recommendation from this comparison.
You want calcium and magnesium taken out of the water that feeds showers, a cylinder or a boiler. The BWT WS355 is the ion-exchange listing at £599, with 4.4 from 98 ratings, tablet salt and a stated 30 L/min. The WRAS and BS 6920 lines print no approval number.
You will not tee into the rising main and you are looking at a clamp-on unit. The Eddy ED6002P-UK is £139, with 4.1 from 452 ratings. The bullets say hardness is unchanged. That review count is not a softening result.
You need one tap that stays on hard water. The NHS says not to make infant formula with artificially softened water, and ion exchange adds sodium. If you still fit a salt unit for the rest of the house, keep that kitchen tap off the softened pipe. The BWT WS355 is the salt listing with the larger UK review count.
The BWT WS355 is the top pick for ion exchange in this set: £599, 4.4 from 98 amazon.co.uk ratings, tablet salt, a stated 30 L/min, and a WRAS and BS 6920 claim with no approval number in the extract. UK reviews also report a failed screen and a paid repair after the labour warranty. The AquaHouse 9 litre is the best value among salt units with a WRAS number printed, at £399.99, 4.6 from 10 ratings, and 583 mm tall. Salt and flexi hoses are extra. The Eddy at £139 is a different type. Its bullets say hardness is unchanged.
AquaHouse 9 litre
£399.99 salt softener, 583 mm tall, with WRAS number 260502718 printed and not re-checked.
Editorial
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.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources from the digest of 16 October 2026, and amazon.co.uk extracts dated 15 October 2026.
This page contains affiliate links. If you buy through them, we may earn a commission at no extra cost to you. The notes use amazon.co.uk listings and public UK sources, not a laboratory test.
