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How to Stop a Leaking Pipe With Water in It
Every guide to soldering says the pipe must be bone dry, and then stops. In a real house the pipe frequently will not drain, because there is no drain-off, no low point, or the run holds water no matter how many taps you open. This is what to do about that.
The Short Answer
You have two choices: stop the water reaching the joint, or use a fitting that does not care. Bread in the pipe, a pipe freezing kit, or a plug tool will hold back a trickle long enough to solder. Or skip the flame entirely and use compression or push-fit, both of which tolerate a damp pipe and give a permanent repair. For most people the second is the right answer and the first is only worth it when a soldered joint is necessary.
First, Try Harder to Drain It
Worth ten minutes before reaching for anything clever, because a properly drained pipe makes every subsequent step easier.
Turn the supply off, then open the lowest tap or draw-off point in the property, and open a high one as well. The high one lets air in, and a pipe with no air path holds its water the way a finger over a straw does. That single point solves a surprising share of stubborn drains.
On a heating circuit there is usually a drain-off cock at a low point, often near the boiler or on a downstairs radiator, that takes a hose. On a cold supply there may be one near the stopcock. Look before assuming there is not.
If the leak is above the joint you want to work on, gravity is working for you and the water will find its way out of the leak itself given time. If it is below, that section will hold water regardless of what you open, and that is the case the rest of this guide is about.
Holding Back a Trickle Long Enough to Solder
Three approaches, in ascending order of cost. All of them are about the same thing: keeping the joint dry for the two or three minutes it takes to get up to temperature and flow the solder.
- Bread. The old trick and it does work. A piece of white bread, crust removed, pushed into the pipe an inch or two upstream of the joint, packs into a temporary plug that holds a trickle. It then dissolves and washes out when the water goes back on. Take the crust off, run the taps well afterwards, and remove any tap aerators or shower heads first so the debris does not lodge in them.
- A pipe freezing kit. A spray canister and a jacket that clamps round the pipe and freezes a plug of ice inside it, giving you a genuinely dry section for a limited window. Effective and controllable, and it is what most plumbers reach for. Follow the instructions on duration, keep the freeze away from any joint you are heating, and note it does not work on a pipe with flow still running through it.
- A mechanical pipe plug or stopper. A tool inserted through an opened end that expands to seal. Only relevant when you have already cut the pipe, so it suits a planned repair rather than an emergency.
The Simpler Answer
For most people doing one repair, the honest advice is to stop trying to solder it. The reason the pipe has to be dry is specific to soldering, and it is not a general requirement of joining pipe.
A compression fitting tolerates a damp pipe entirely. Clean the pipe end, cut it square, deburr it, slide on the nut and olive, and tighten. A slow weep of water while you assemble it does not affect the joint at all. Once it is tightened the joint seals and you are finished.
Push-fit is the same story with even less effort, provided the pipe end is square, deburred and pushed fully home, with an insert where the pipe is plastic. Water present while you make the joint is not a problem.
Both are permanent repairs rather than temporary ones, which is worth stating plainly because the assumption that soldering is the real fix and everything else is a bodge is widespread and wrong. The reasons a plumber often solders are neatness, compactness in tight spaces, and cost across many joints. None of those matter when you are fixing one pipe under a sink.
So the sequence worth following is: try to drain it properly, and if it will not drain, use a mechanical fitting. Reach for bread and freezing kits only when a soldered joint is genuinely required, which for a homeowner is rare.
Getting Water Back On Afterwards
A step people rush and then regret, particularly after using bread.
Take off any tap aerators, shower heads and washing machine inlet filters before restoring the supply. Bread residue and any debris disturbed during the work will travel to exactly those places and block them, and clearing a blocked aerator is fiddly compared with unscrewing it beforehand.
Open a tap and let the supply back on slowly rather than all at once. A rapid refill sends a pressure surge through the system that can find weaknesses elsewhere, which is how one repair occasionally produces a second leak in a different room.
Run the cold taps until the water runs clear and steady with no spluttering, which means the air is out. Then check your joint, dry it with a cloth, and look again after ten minutes. A weep shows as a bead on a dry surface well before it drips.
And refit everything you took off. An aerator left off is a minor thing until somebody notices the tap splashing across the sink for a month.
When the Pipe Will Not Stop Running At All
If water is flowing rather than trickling and nothing you do reduces it, the supply is not actually off, and that is the problem to solve rather than working around.
The usual causes are a stopcock that is turning but no longer sealing internally, which is common on old valves that have not been moved in decades, or a second supply route into the property that has not been isolated. Both mean you are trying to repair a live pipe, which will not succeed.
A stopcock that turns fully and does not stop the flow needs replacing, and doing so requires the supply isolated further back, at the external stop valve. In a flat that valve may be shared, and it may be inside a locked communal cupboard. That is the point at which this stops being a job to push through on a Saturday.
Turning the water off further back is also the only safe way to work on the stopcock itself, so if the stopcock is the problem, that is the call to make rather than the repair to attempt.
Why the Pipe Often Will Not Drain Here
This problem is more common in Glasgow's older flats than in a modern house, and for a reason that is nothing to do with the plumbing being poor. Pipework retrofitted into a building that never had any gets routed wherever it could go, threaded through joists and around structure, and a run installed that way frequently has no consistent fall and no low-point drain-off. It holds water in dips because it was never laid to drain.
So the standard instruction to open the lowest tap often does very little, because the water is not sitting at the lowest tap. It is sitting in a belly in the run under a floor, and it will stay there while you stand at a blowtorch wondering why the joint will not heat.
Flats compound it. In a top floor flat there may be no draw-off point below the run at all, so there is nowhere for the water to go. Meanwhile the shared cold supply riser serving the close means that isolating your own flat does not necessarily empty everything you can see, and pipework can refill from a direction you did not expect.
The practical conclusion for this housing stock is the same as the one above but with more force: mechanical fittings are usually the right choice in these buildings, and the professional habit of using compression and press fittings in tenement floor voids exists because of exactly this combination of undrainable runs and enclosed timber spaces.
When to Call Someone Out
Worth calling when the supply will not shut off properly, when the stopcock turns without stopping the flow, or when the only isolation point is a shared valve you cannot reach. Those are not stubbornness problems, they are a different job. Also worth it if a run keeps refilling from somewhere and you cannot work out where, since that usually means a supply route nobody has mapped. Mo, Kyle or Matt cover this, and they will generally use a mechanical fitting in an undrainable spot rather than fighting the water, which is the same advice as above with the right tools behind it.
Leak Detection in GlasgowCommon Questions
It does, and it has been used by plumbers for decades, so it is not folklore. Its limits are worth knowing: it holds a trickle rather than a flow, it buys minutes rather than an hour, and it fails without warning as it softens. It is also the reason to prefer a mechanical fitting where you can, since a compression joint simply does not care about the water and needs no trick at all.
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“Our radiator pipe was bent and leaking. They answered straight away… Guy was here an hour later and he was wearing ID, very professional, patient and kind. We just got a new carpet in this room and he done an amazing job on getting little to no water on it. Couldn't recommend enough, price was reasonable.”
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Jemma M. · Glasgow
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“As a small business owner, I needed a drainage company that could respond quickly. The team attended first thing in the morning, cleared the blocked drain and carried out a full CCTV survey. All documentation emailed across promptly. Professional, efficient and great value for money.”
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Read Next
Full guide
How to Repair a Leaky Pipe
Turn the water off first, then find out what the pipe is.
How to Solder Copper Plumbing
Clean the pipe end and the inside of the fitting until both are bright, flux both, assemble, and heat the fitting rather than the solder until the solder is drawn into the joint by capillary action.
How to Fix a Leaking Pipe Joint
Identify the joint type first.
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