Why Plumbing Checks Matter
Plumbing defects are the defects most likely to cause serious, expensive damage. A slow weep from a radiator valve, a waste trap that is not tight, or a flexi-pipe that has not been fully tightened can ruin a ceiling, floor, or fitted unit within weeks. The signs are subtle on day one, which is exactly why a systematic plumbing check — running water long enough to reveal leaks — is one of the most valuable parts of a snagging inspection.
Use this checklist with the full new build snagging checklist and the bathroom and kitchen room guides.
How to Test Plumbing
Run water for long enough to fill every trap and put joints under pressure — a minute or two per fitting, not a quick splash. Then check the connections, the cupboard bases, and the ceilings below with a dry tissue. Look for damp, discolouration, or a musty smell that hints at a hidden leak.
What to Check
Taps, wastes and traps
- Hot and cold are the correct way round (hot left, cold right).
- Taps operate smoothly and stop dripping after shut-off.
- Wastes drain freely with no gurgling or slow run-off.
- Traps are tight — no damp beneath sinks or basins.
- Overflow pipes are fitted and discharge correctly.
Toilets
- WC is secure with no movement.
- Flush is full and effective; cistern refills and stops.
- No water on the floor around the base.
- Isolation valve (if fitted) is accessible and operates.
- Pan and cistern are not cracked or chipped.
Radiators and heating
- Every radiator gets hot across the whole surface (no cold spots).
- No air in the system — bleed if needed, but log if a radiator needs repeated bleeding.
- Radiator valves operate and do not weep.
- TRVs (thermostatic valves) are fitted and turn freely.
- No damp patches on walls behind radiators.
Boiler and hot water
- Boiler fires and heats water on demand.
- Pressure gauge reads in the green band (typically 1–1.5 bar).
- No error codes displayed on the boiler.
- Flue is fitted and sealed externally.
- Boiler commissioning certificate and warranty registration received.
Common Plumbing Defects
The most common plumbing defects are weeping radiator valves, traps not fully tightened, cold spots in radiators (air in the system), and dripping taps. A leaking waste or supply joint is the highest-impact defect — it causes ceiling and floor damage quickly. Report any sign of damp the same day.
For the wider set of defects, see common new build defects.
Plumbing Snag Checklist
Work through each section, tick items off as you check them, and export a clean printable PDF to take with you on the day.
Taps, Wastes & Traps
Toilets
Radiators & Heating
Boiler & Hot Water
Check the ceilings below any upstairs fitting for damp. A slow weep from a trap or valve is the plumbing defect most likely to cause serious damage.
Frequently Asked Questions
Snag Your Plumbing with Snagr
Snagr turns your phone into a professional snagging tool. Capture every defect, generate branded PDF reports and track repairs through to completion — all from one app.
Continue Reading
Related Snagr guides to help you inspect and protect your new-build home.
Common New Build Defects
Leaking joints are among the most common — and most damaging — defects.
Read Guide