Summary

Drips and splutters are the two most common tap symptoms a tradesperson is called out for. They're cheap, fast jobs — but only if you diagnose correctly the first time. The temptation is to replace the entire tap and bill £150 because "tap is faulty"; the correct fix is usually a £4 cartridge and 15 minutes. Customers know this difference and a quick washer-change at a fair price builds repeat business and reviews.

This article is a structured decision tree for both faults, covering compression-style (rubber washer) and modern quarter-turn (ceramic disc cartridge) taps, mixers, and electronic / non-concussive types. It also covers when the fault is NOT in the tap — partially closed isolation valve, failed PRV (pressure reducing valve), air-locked supply, blocked aerator, and DHW supply problems.

Key Facts

Quick Reference Table

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Symptom Most likely cause Fix
Constant drip when off, compression tap Worn washer Replace washer (£1, 15 min)
Constant drip when off, ceramic tap Damaged disc / cartridge Replace cartridge (£4–20, 20 min)
Drip from spout when off, mixer tap Damaged cartridge Replace cartridge
Drip from base of spindle (compression) Worn O-ring or gland packing Replace O-ring
Splutter on first turn, then clears Air in supply — recent work Purge — fully open for 1–2 min
Persistent splutter, weak flow Blocked aerator Unscrew aerator and descale
Splutter on hot only, cold steady Air in cylinder / combi DHW Bleed cylinder, check combi DHW
Splutter on cold only Partially blocked aerator OR partially closed isolation valve Check both
No flow / very weak Closed/failed isolation valve, scaled stop tap, supply problem Trace upstream

Detailed Guidance

Diagnosing a constant drip

Tap dripping with handle closed?
├── Compression tap (rises when turning)
│     ├── Drip from spout → Worn washer at base of spindle
│     │       → Isolate, unscrew tap head, remove spindle, replace washer
│     ├── Drip from spindle base → Worn O-ring / gland packing
│     │       → Replace O-ring or re-pack gland
│     └── Drip won't stop with new washer → Damaged seat
│             → Re-cut seat with seating tool OR replace tap
└── Ceramic disc cartridge (quarter-turn)
      ├── Drip from spout → Cartridge damaged / scaled
      │       → Identify cartridge size, replace whole cartridge
      └── Drip from base → Body O-rings
              → Replace O-rings or full tap if not serviceable

Diagnosing splutter

Tap splutters or surges?
├── Both hot and cold splutter
│     ├── Recent work (new pipework, stop-tap closed) → Air in system
│     │       → Open all taps fully, top floor up, for 2 min
│     └── Persistent splutter, no recent work → Failed PRV or supply problem
│             → Check inlet pressure, check PRV operation
├── Hot only splutters
│     ├── Unvented cylinder → Air lock at top, or expansion vessel failure
│     │       → Bleed cylinder air vent, check expansion vessel pressure
│     ├── Combi boiler DHW → Modulation problem, scaled HEX
│     │       → DHW service / descale
│     └── Vented cylinder → Air entering via vent pipe
│             → Check cold feed and vent pipe positions
├── Cold only splutters
│     ├── Weak flow as well → Partially blocked aerator
│     │       → Unscrew, descale in citric acid, reinstall
│     ├── Strong flow but splutter → Partially closed isolation valve
│     │       → Open isolation valve fully (slot parallel to pipe)
│     └── Other taps fine → Local pipe air pocket
│             → Open tap fully, leave for 5 min to purge

Replacing a ceramic cartridge

  1. Isolate the supply at the isolation valve under the basin/sink. Slot perpendicular to pipe = closed.
  2. Open the tap to release residual pressure and confirm isolation.
  3. Pop off the handle cap (small flat screwdriver, careful — chrome scratches easily).
  4. Undo the handle screw — usually a 2.5mm or 3mm hex grub screw.
  5. Lift handle off, exposing the cartridge body.
  6. Unscrew the cartridge retaining nut with the correct-size spanner (avoid grips — they round the brass).
  7. Lift out the cartridge. Note the alignment notches (cartridges are keyed to ensure hot/cold are correct).
  8. Match the new cartridge: same diameter, same height, same spline count on the splined drive.
  9. Reverse the assembly. Test before sealing the customer back up.

Replacing a compression washer

  1. Isolate the supply.
  2. Open the tap to release pressure.
  3. Unscrew the cover/shroud at the top of the tap to access the headgear.
  4. Loosen the body nut at the base of the headgear with a wrench (anti-clockwise).
  5. Lift out the headgear, exposing the spindle and washer.
  6. Hold the spindle in soft grips, undo the small brass washer-retaining nut at the very bottom.
  7. Remove old washer, fit new same-size (typically 12mm or 15mm).
  8. Reassemble. Test before signing off.

When to replace the whole tap

Otherwise, repair beats replace 9 times out of 10 on a domestic tap.

Frequently Asked Questions

How long should a tap last?

A quality ceramic disc tap should run for 10–15 years before cartridge replacement. Cheap supermarket taps may need a cartridge in 3–5 years. Compression taps with rubber washers historically lasted 30+ years with periodic washer changes — they're slower to use but more serviceable than modern cartridge designs.

Can I use a different brand's cartridge?

Sometimes. Cartridges are not standardised — many manufacturers have proprietary spline and dimension combinations. Hansgrohe, Bristan, Grohe, and Vado each have their own. Generic "universal" cartridges fit common 35mm and 40mm sizes but may not seat perfectly. Always try to match the brand if known.

Why does my customer's tap drip overnight but not during the day?

Usually a partial seal — works under steady pressure (day = mains use elsewhere drops pressure slightly) but leaks under high static pressure (night = no demand = full mains pressure). The cartridge or washer is starting to fail. Replace before it gets worse.

What's the WRAS approval for?

The Water Regulations Approval Scheme certifies that a tap or fitting meets the Water Supply (Water Fittings) Regulations 1999 — specifically around backflow prevention and material safety (no harmful leaching into drinking water). Always specify WRAS-approved taps on potable supplies. Non-approved taps imported online may fail water company inspection and have to be removed.

Should I quote a fixed price or hourly for a washer change?

Fixed price. A washer change is 15–30 minutes including travel, with predictable parts cost. £45–85 is the standard range. Hourly rate billing on a 15-minute job feels unfair to customers and damages your future-job conversion rate.

Regulations & Standards