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A dripping tap is the most common plumbing job there is — and in Thames Water’s hard-water region, limescale is often the culprit, not a whole new tap. Whether it’s a repair or a new mixer, the trick is checking what actually failed before spending on parts.
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On this page
Tap types and why it matters · Fixing a dripping tap · Low flow and hard water · What a plumber checks before a swap · Installing a new tap · Outside taps · What it costs in Forest Hill — 2026 · Why verified plumbers · FAQTap types and why it matters
The fix depends on the tap. Traditional compression taps seal with a rubber washer that wears — the classic drip. Modern ceramic-disc taps use a cartridge that lasts longer but fails harder over time, especially in hard water. Monobloc and mixer taps combine hot and cold in one body and often have small-bore “tails” that need the right connectors. Knowing which you have tells you whether it’s a 50p washer, a cartridge, or a full replacement — and stops you being sold a new tap when a part would do. The replacement also has to match the property’s pressure system: an older gravity-fed hot side needs a different mixer choice from a newer mains-pressure flat.
Fixing a dripping tap
A drip from the spout is a worn washer (compression tap) or a worn ceramic cartridge (mixer/disc tap) — a cheap part in both cases. A drip or weep from the base or handle is usually a perished O-ring or gland, again a small part. What makes a repair fail is limescale: in this Thames Water hard-water area, seats and cartridges scale up, so a good plumber cleans or replaces the seat, not just the washer, or the drip returns in weeks.
Low flow and hard water
A tap that’s lost pressure is usually not a mains problem — it’s a scaled or blocked aerator (the mesh nozzle on the spout), which unscrews and cleans or replaces in minutes. If it’s more than one tap, or the whole cold side, Thames Water’s own check is useful: it notes that water normally enters at the cold kitchen tap, so if that runs but others are weak, the issue is your internal plumbing rather than the network¹. Hard water is a Thames Water regional issue rather than a Forest Hill-only one — Thames Water confirms all the water in its region is hard because it passes through chalky limestone², and scale slowly narrows tap workings and aerators. In a converted flat or a flat above a local parade, weak flow can also trace to a half-closed isolation valve hidden behind fitted units or boxed pipework, so access matters as much as the tap.
What a plumber checks before a swap
A thorough plumber doesn’t just swap the tap — before touching it they test the cold kitchen tap, remove or clean the aerator, check the isolation valves under the basin or sink (so the whole house doesn’t need turning off, and to confirm they actually shut), check the water pressure (some mixers and monoblocs need a minimum pressure to work properly), inspect the cartridge or washer, the flexi tails and connectors, and confirm where the stop tap is in case an isolation valve is seized. In some older Forest Hill terraces and conversions, seized stopcocks and stiff isolation valves can turn a quick tap change into a valve job first; in flats, tap tails may sit behind fitted units or boxed-in pipework; in newer SE23 flats, monobloc mixers and concealed plumbing make access and pressure suitability the main check. A gravity or low-pressure system needs a compatible mixer, while mains pressure gives more choice. If the cartridge is obsolete, the seat is corroded, the tap body is seized, the flexi tails are failing or the valves are inaccessible, replacement can be more economical than repair — better known before the job than during it.
Installing a new tap
Fitting a new tap connects straight to your drinking-water supply, so it falls under the Water Supply (Water Fittings) Regulations. One good way to stay compliant, especially for new or higher-risk fittings, is to use an approved plumber: WaterSafe is the industry-backed national directory whose approved plumbers are trained in the Water Fittings Regulations and can issue a Certificate of Compliance³. That is not the only lawful route for a simple tap repair, but it matters where fittings carry a backflow risk — a pull-out spray tap, an outside tap, or a tap feeding into an appliance, for example. Choose fittings suitable for drinking-water use, match the replacement to the property’s pressure system and connection type, and where relevant look for WRAS-approved or water-regulation-compliant products. Fitting new isolation valves at the same time is worth it: the next repair becomes a two-minute job instead of a house shut-down.
Outside taps
An outside tap is a popular add-on, but it’s a backflow point — a hose left in a water butt or a bucket of chemicals can siphon back toward the supply. The Water Fittings Regulations treat it as needing backflow protection, typically a double check valve fitted on the supply, which a competent plumber should install as standard. The same backflow check matters for pull-out spray taps and appliance-fed fittings. It’s a small job done properly, or a contamination risk done cheaply.
What tap work costs in Forest Hill — 2026
Editorial estimate only — not official pricing, and no substitute for a written quote.
| Job | Typical range |
|---|---|
| Re-washer / re-seat a dripping tap | £70–£140 |
| Replace ceramic cartridge | £80–£160 |
| Replace kitchen or basin tap (like-for-like) | £90–£200 |
| Fit new mixer / monobloc tap | £120–£280 |
| Clean / replace aerator | £50–£90 |
| Replace seized isolation valve | £80–£160 |
| Fit outside tap + double check valve | £120–£250 |
Ask whether isolation valves are included — fitting them makes every future repair cheaper.
Why verified plumbers in Forest Hill
Tap work connects to your drinking water, so competence and compliance matter even on a small job. Every plumber listed here is checked before they appear — identity, insurance and trading presence, with Gas Safe registration where any gas work is involved — and re-checked annually. A flat monthly listing fee means no customer-side fee and no pay-to-play ranking. For new fittings, higher-risk fittings or backflow-sensitive work, it is worth considering a WaterSafe-approved plumber; listing checks are administrative and don’t replace your own checks or guarantee workmanship. See how we verify plumbers.
Frequently asked questions
Usually limescale on the seat. In Thames Water’s hard-water region, the seat scales up and chews through washers, so the seat needs cleaning or replacing, not just the washer.
Most often it’s a scaled aerator on the spout, which cleans in minutes. If several taps or the whole cold side are weak, it’s more likely internal plumbing than the network — the cold kitchen tap is the one to test.
It connects to drinking water and can carry a backflow risk, so for spray taps, outside taps or appliance-fed taps it is worth considering a WaterSafe-approved plumber. For any new tap, use fittings suitable for drinking-water use and fit isolation valves at the same time where needed.
So the next repair only shuts off that tap, not the whole house — and so a future plumber isn’t hunting for a seized stopcock. They’re cheap to fit during other work.
No, but it needs backflow protection (a double check valve) under the Water Fittings Regulations. Done properly it’s straightforward; done without the valve it’s a contamination risk.
Tap repair across Lewisham — areas we cover
Tap Repair Forest Hill · Honor Oak · Sydenham · Perry Vale · Crofton Park · CatfordRelated services in Forest Hill
General Plumbing · Kitchen Plumbing · Bathroom Plumbing · Toilet RepairsRelated guides
London Hard Water Guide · Find Your Stop Tap · How to Read a Plumbing QuoteSource provenance
Guidance on this page is drawn from primary UK sources: Thames Water (the cold-kitchen-tap diagnostic for internal-plumbing pressure issues and the hard-water region) and WaterSafe (the approved-plumber route and Water Fittings Regulations compliance, including backflow protection). Cost figures are an editorial estimate only, and local observations are editorial context.
Sources & further reading
¹ Thames Water — No water or low pressure: https://www.thameswater.co.uk/help/water-and-waste-help/no-water-or-low-pressure
² Thames Water — Hard water: https://www.thameswater.co.uk/help/water-and-waste-help/water-quality/hard-water
³ WaterSafe — Find a local approved plumber: https://www.watersafe.org.uk/
Last reviewed: July 2026 by Adiel Khan — SFEDI-accredited business advisor, 20+ years’ experience (South East Enterprise Ltd) and operator of VerifiedPlumbers. LinkedIn ↗. This page is checked for compliance and regulatory accuracy against Thames Water and WaterSafe guidance. Source links are provided within the page where relevant.