Leak Detection in Welwyn
Find the leak before you start lifting floors
The worst thing you can do with a hidden leak is guess. Guessing means a hole in a ceiling, a lifted floor and a bill, and quite often the water was coming from somewhere else entirely.
Vantage Plumbing and Heating traces leaks in Welwyn and the surrounding AL6 villages using non invasive equipment: thermal imaging, acoustic listening and correlation, tracer gas and moisture metering. We are Gas Safe registered, reg. 956889, we work out of Stevenage, and we run a genuine 24 hour line every day of the year.
A note on the name, because it matters when we are routing an engineer: this is Welwyn village, the old settlement on the River Mimram, AL6 9 and AL6 0. Welwyn Garden City is a separate town about a mile south. A leak in a Georgian cottage off Church Street behaves nothing like a leak in a Garden City semi.
The ground under Welwyn, and why it changes how a leak behaves
The River Mimram, a chalk stream, runs straight through the middle of the village. It rises from a spring up near Whitwell, comes through the village under Singlers Bridge and the High Street and Mill Lane bridges, then disappears into culverts beneath the bypass and the A1(M) before re emerging at Lockleys Park and continuing through Tewin Water towards Panshanger and the Lea at Hertford.
That matters for leak detection in three practical ways.
First, the ground here already moves water about. On the valley floor you cannot assume that damp at low level is a burst pipe, and you cannot assume it is not. A moisture reading alone proves nothing. What proves something is finding the source, which is why we test before we cut.
Second, there is slope in this valley. Water escaping from a supply pipe or a heating circuit does not sit above the leak. It runs under a screed, along a joist or down a cavity and shows up somewhere that has nothing to do with where the pipe failed. Acoustic tracing and thermal imaging find the pipe.
Third, there is a great deal of buried infrastructure in this area, some of it very old. The Roman baths at Dicket Mead sit in a vault nine metres below the A1(M) at Junction 6, a fair reminder that not everything under the ground around Welwyn is on a drawing. We survey rather than assume. What we will not do is tell you what the subsoil under your particular garden is, because we have not seen verified mapping for the village.
Your mains supply comes from Affinity Water’s Central region and your wastewater is Thames Water’s responsibility. Both matter when a leak turns into a question of who pays for what.
The first sign is usually the bill
Most of the leaks we find in Welwyn were not discovered by anybody seeing water. They were discovered by a water bill that went up for no reason, or a meter that keeps counting after every tap in the house is closed.
Other early signs worth acting on: a boiler that keeps losing pressure and needs topping up every week or two, an area of floor that is warmer than the floor around it, a musty smell in a room with nothing visibly wrong, a patch of plaster that will not dry out no matter how long the heating is on, and unusually green grass in one spot of an otherwise ordinary lawn.
How we actually find it
Thermal imaging. A thermal camera does not see water. It sees temperature difference. That makes it superb for tracing heating pipework and underfloor heating circuits under screed, because a leaking hot circuit paints a picture on the floor surface, and it is very useful for mapping how far moisture has spread through a structure.
Acoustic detection and correlation. A pressurised leak makes a noise, and with ground microphones and correlators that noise can be located along a buried pipe run to within a small margin. This is the technique for supply pipe leaks between the boundary and the house, which is exactly the run that fails on properties down the long drives around Harmer Green and Rabley Heath. It works best on metal pipe. On runs of modern plastic supply pipe, which carries sound poorly, tracer gas is used instead.
Tracer gas. Where a pipe is empty, buried deep or in a difficult material, we introduce a safe hydrogen and nitrogen mix into the isolated pipework and detect where it escapes to the surface. It is the most definitive method we have and it is what we reach for when a leak has already defeated somebody else.
Moisture meters and pressure testing. Straightforward, and still the fastest way of proving whether the escape is coming from the supply, the heating, or from something that is not a plumbing leak at all.
Leaks that turn out not to be leaks
A significant proportion of the calls we take in Welwyn are not pipe failures.
Shower trays and wet rooms are the classic. Water is getting through the seal at the edge of the tray, or through a failed grout or silicone line, or under a badly formed wet room floor, and it appears on the ceiling below looking exactly like a burst pipe. The fix is a sealing repair, not a plumbing repair, and it costs a fraction of the price.
Waste and soil connections behind panels. A slow weep from a pan connector or a bath trap only shows itself when the fitting is used, which is why it can be dry when you look at it.
Roof and rainwater failures. A blocked gutter, a slipped tile or a failed lead flashing puts water inside a wall in a way that looks entirely internal. On older properties with parapet detailing this is far more common than people assume.
Condensation and cold bridging in solid walled properties. A wall that is wet in winter and dry in summer is telling you something other than a pipe has burst.
We would rather tell you it is your shower seal and charge you for a detection visit than sell you a leak repair you do not need.
The Welwyn properties where leaks are hardest to find
The historic core, Mill Lane and the High Street. Solid floors laid over earlier solid floors, pipework buried at some point in the last hundred years by somebody who did not record it, and rooms that have been reconfigured more than once. There is no drawing. There is only tracing.
Properties around Digswell and the viaduct valley. The Digswell Viaduct has carried the railway across the Mimram valley on around forty brick arches since 1850, which gives you a sense of how much fall there is across this ground. On sloping sites, water from a leak travels a long way before it shows, and it usually shows at the lowest point of the building rather than at the pipe.
Extended houses out towards Tewin and Ayot St Peter. Every extension is a joint between old pipework and new, often with the joint buried under a new floor. That junction is where a disproportionate number of under floor leaks occur, and it is the first place we look on a property that has been added to.
Anywhere with underfloor heating. Increasingly common in Welwyn extensions and conversions. A pinhole in a buried circuit is undetectable by eye and unfindable by guesswork, and it is precisely the job thermal imaging was made for. We isolate circuits one at a time, pressure test each and image the floor, so you get told which loop and roughly where, rather than being advised to dig the whole room up.
Old supply pipes, and who is responsible for what
The oldest properties in the village can still have lead supply pipe, and iron pipework turns up as well. Both fail eventually, and iron in particular corrodes from the inside until the wall thickness gives up.
The important thing to understand is ownership. The private supply pipe running from the boundary stop tap into your home is your responsibility as the property owner, not the water company’s. If the leak is on that run, it is your repair. Cover for an external underground supply pipe is often an optional extra rather than something every policy includes, so check your schedule rather than assume. We locate the leak accurately so that the repair is a short excavation at a known point rather than a trench across the whole drive.
Insurance claims and trace and access
Trace and access cover is the part that pays for finding the leak and putting right the damage caused by getting at it. It is not the same thing as cover for the failed pipe, and the two are treated separately in most wordings.
We hold no relationship with any insurer, so we won’t be telling you what your policy covers. Read through your schedule for the trace and access section and confirm the position with your insurer before you commit to the job. What we do is produce the report your insurer asks for, with the findings, the method used and thermal images where they are relevant. If you are claiming, say so when you book and we will document the job properly from the start.
Trusted & Accredited Professionals
What it costs
Detection is priced as a fixed visit rather than an open ended hourly rate, so you know what the investigation costs before you commit. What we cannot price blind is the repair, because until the leak is found nobody honestly knows what the repair is. Once we have located it, you get a price for putting it right and you are free to have anybody do that work.
Where a leak is found quickly and the repair is small, we will very often do both in the same visit.
Related work in Welwyn
Finding the leak is usually the start rather than the end. We repair supply pipes, replace lead and old iron runs, reroute buried heating pipework that is not worth saving, rebuild shower trays and tanking properly, and carry out drainage investigation where the water turns out to be coming from a drain. Power flushing, boiler work and bathroom work in the village all come from the same team, so nothing is lost handing over between firms.
Areas we cover for leak detection around Welwyn
Welwyn village, Digswell, Tewin, Harmer Green, Mardley Heath, Oaklands, Rabley Heath, Woolmer Green, Ayot St Lawrence, Ayot St Peter and Knebworth, along with Welwyn Garden City to the south. If you are on one of the lanes between them, we still come.
Nearby: Leak detection in Knebworth · Leak detection in Codicote · Leak detection in Hatfield
For general plumbing rather than a detection survey, see our Welwyn plumbing page.
Why Choose Vantage?
With a 4.9 rating on Google and more than 700 reviews across Google, Checkatrade and Trustatrader, fully qualified and accredited engineers, transparent pricing, and a 2-year labour guarantee on every job, Vantage delivers reliable, high-quality workmanship you can trust with fast response times, and genuine local service.
- Five-star Google reviews
- Gas Safe Registered No. 956889
- CHAS Registered
- City & Guilds qualified
- Checkatrade approved
- 2 year labour guarantee on every job
- Fully stocked vans most jobs fixed on the first visit
- Established local business with a dedicated office team and multiple qualified engineers
- No job too small
- Transparent pricing with a fixed price provided before any work begins
- 700+ reviews across Google, Checkatrade and Trustatrader, 4.9 on Google
Frequently Asked Questions
Will you have to dig up my floor to find the leak?
No. The whole point of the equipment is to find the leak first, so that any opening up is small and in the right place.
My water bill has jumped but I cannot see any water. Is that a leak?
Very often, yes. Turn everything off and watch the meter. If it is still moving, something is running somewhere, and that is worth tracing before it finds its way into a floor.
Can you find a leak in underfloor heating?
Yes. We isolate and pressure test each circuit and use thermal imaging over the floor to identify which loop has failed and where.
Is a leak on the pipe in my garden my responsibility?
If it is on the private supply pipe between the boundary stop tap and the house, yes. Whether it is covered depends on your policy, so check your schedule.
Does my insurance pay for the detection work?
That is your insurer’s decision, not ours. Check whether your schedule includes trace and access and confirm with them before you commit to any work. We produce the report they ask for.
Do you cover Welwyn Garden City too?
Yes, but as a separate area. This page is about Welwyn village in AL6, which is a different place with much older building stock.
Get a leak traced in Welwyn
Call 01462 506374. We will find it properly, tell you exactly what we found, and give you a price to put it right.