Water filters for the home: which type is worth it?
For most London homes the filter worth having is an under-sink unit feeding a separate drinking-water tap: it deals with the chlorine taste people usually complain about, costs little to run and leaves the rest of the plumbing alone. A whole-house filter is worth it when the problem affects every outlet, such as sediment after mains work, or when you want chlorine removed from showers and baths too. Reverse osmosis is for people who want mineral-stripped water and accept the waste water, the space and the maintenance. No ordinary filter removes hardness from the whole house; that is a softener's job.
Loyal Plumbers · Updated
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Mains water in London is treated to drinking water standards before it reaches your stop valve, and the Drinking Water Inspectorate checks that the suppliers meet them. A filter is therefore not a safety device for most homes. It is a way of changing something specific: taste, smell, particles, or one known contaminant such as lead from old pipework.
Being precise about the problem stops you paying for treatment you do not need. A chlorine taste at the kitchen tap is a small, local job. Brown water from every tap after street works is a supply question for your water company first. Limescale on the shower screen is hardness, which filters mostly do not touch.
- Chlorine taste or smell at the drinking tap: under-sink carbon filter
- Sediment, grit or discoloured water throughout the house: whole-house sediment filter, after the supplier has been told
- Chlorine in showers and baths as well as drinking water: whole-house carbon filter
- Very low mineral content for drinking or aquariums: reverse osmosis at one tap
- Limescale on taps, showers and appliances: a softener or scale reducer, not a filter
The main types of home water filter compared
The types differ in where they sit, how much water they treat and how much plumbing they need. The table covers the options people usually weigh up.
| Type | Treats | Plumbing involved | Main drawback |
|---|---|---|---|
| Jug or tap-mounted | Water you pour through it | None | Small volumes, frequent cartridge changes |
| Under-sink with filter tap | Drinking and cooking water at one tap | Tee off the cold supply, separate tap on the sink or worktop | Needs cupboard space and access for cartridge changes |
| Whole-house (point of entry) | Every hot and cold outlet | Housing on the incoming main after the stop valve, with isolation and a bypass | Must be sized for flow; can reduce pressure if undersized or neglected |
| Reverse osmosis | Drinking water at one tap | Cold feed, drain connection, storage vessel, dedicated tap | Sends some water to drain; slow output; more parts to maintain |
When a whole-house filter is worth it
A whole-house filter makes sense when the thing you want to change turns up at every outlet. The commonest case is sediment: fine particles that block tap aerators, shower heads, appliance inlet screens and thermostatic cartridges. A sediment stage protects those fittings and is simple to maintain. A carbon stage added after it removes chlorine from the whole supply, which some people want for showering and bathing.
It is less worth it if your only complaint is the taste of drinking water. You would be filtering water for the toilets, the washing machine and the garden tap to improve one glass at the kitchen sink. An under-sink filter does that job for a fraction of the size and upkeep.
Remember that the chlorine in mains water is there to keep it safe on the way to you. Once a whole-house carbon filter takes it out, the water inside your own pipework no longer carries that protection. That is a reason to keep up with cartridge changes, and to ask before fitting carbon filtration ahead of a cold water storage tank where water can sit for a long time.
If sediment or discoloured water appears suddenly, report it to your water supplier before fitting anything. It often follows mains repairs or a change in flow in the street, and the supplier needs to know.
Reverse osmosis: when it fits and when it does not
Reverse osmosis pushes water through a very fine membrane and removes most dissolved minerals as well as chlorine and many other substances. It is the one domestic filter that also removes hardness, but only at the single tap it serves. The rest of the house is unchanged.
The trade-offs are practical. Part of the water goes to drain to flush the membrane, output is slow enough that most systems include a small storage vessel, and there are several cartridges and a membrane to replace on schedule. The unit needs a cold supply, a drain connection and room under the sink. A treatment unit that discharges waste water is normally notifiable to the water supplier before it is installed, so it is not a casual DIY fit.
Lead pipes: a filter is a stopgap
Some older London homes still have a lead supply pipe or lead pipework indoors. Filters certified for lead reduction can lower the lead reaching one tap, and that is a sensible short-term step while you plan the proper fix. The long-term answer is replacing the lead pipework, because the filter only protects the tap it serves and only while the cartridge is in date.
If you are not sure whether you have lead, look at the pipe where it enters the house by the stop valve. Lead is dull grey, soft enough to scratch to a silver shine, and has rounded swollen joints rather than soldered fittings. Your water supplier can also advise.
Upkeep: the part people underestimate
Every filter needs its cartridge changed on the manufacturer's schedule, and some need it more often if the water carries a lot of sediment. A clogged sediment cartridge reduces flow at every tap in the house. An old carbon cartridge stops removing taste and can become a place for bacteria to grow. Before choosing a unit, check what the replacement cartridges cost, how easy they are to buy and whether you can reach the housing without emptying a cupboard.
Write the change date on the housing or in your phone. It sounds basic, but an overdue cartridge is the usual reason a filter that worked well in the first year disappoints in the third.
What a proper installation includes
An under-sink filter is teed off the cold supply with an isolation valve, and the filtered water goes to its own tap so the main kitchen tap keeps working normally. A whole-house unit goes on the incoming main after the stop valve, with valves either side of the housing and a bypass so the house still has water while the cartridge is changed or if the unit fails. It needs to be sized for the flow the house actually draws, or showers and a combi boiler can suffer.
Any installation must meet the water fittings regulations, including suitable backflow protection. Units that backwash or send water to drain need a drain connection and are usually notifiable to the supplier. If you also have or plan a water softener, the order of the units and the position of the drinking water branch need planning together.
Getting a filter plumbed in
Loyal Plumbers carries out general and kitchen plumbing across London and everywhere inside the M25, including plumbing in water treatment units with the isolation, bypass and drain connections they need. We can fit a filter you have already chosen, or look at the supply, the space by your stop valve and the problem you want to solve, and tell you which type makes sense.
Call us or send an enquiry with the filter type or model, where your stop valve is, and what you want the filter to change.
Common questions
- Is it worth filtering tap water in London?
- London tap water is treated to drinking standards, so filtering is about taste, particles or a specific concern such as lead pipes. An under-sink carbon filter is the usual choice if chlorine taste is the complaint.
- Does a water filter remove limescale?
- Most filters do not remove hardness. Reverse osmosis does, but only at the tap it serves. For scale across the house you need a water softener or a scale reducer.
- Will a whole-house water filter reduce my water pressure?
- A correctly sized unit with a clean cartridge should cause only a small drop. An undersized housing or a blocked sediment cartridge can reduce flow noticeably at every outlet.
- How often do water filter cartridges need changing?
- Follow the manufacturer's interval, which varies by type and how much water you use. Sediment cartridges may need changing sooner if your supply carries a lot of particles.
- Can I fit a water filter myself?
- Jug and tap-mounted filters, yes. Under-sink and whole-house units connect to the mains and must meet the water fittings regulations, and units that discharge to drain are usually notifiable to the water supplier.
Sources and further reading
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