No water or very low pressure in the house: quick checks before you call a plumber
- Checked September 2026
- 5 min read
- By PROS AI editorial team
Quick answer
The short version, before the detail.
Run the cold kitchen tap first: it is fed straight from the mains, so if it runs and nothing else does, the problem is inside your plumbing. If it is dry too, check that your stopcock is fully open and ask a neighbour. Thames Water's mains and the pipe to your boundary are theirs to fix; everything from the boundary inwards is yours. Most no-water calls in London end at a half-closed stopcock, a frozen pipe or a street-wide outage, none of which needs a plumber.
What is the likely cause?
Most common first, with how to tell.
Planned work or a burst main in the street.
How to tell: the neighbours are dry too, or Thames Water's network map shows an incident for your postcode.
The stopcock is partly closed or seized.
How to tell: a trickle at every tap rather than nothing, often after a plumber's visit or a knock under the sink. The valve opens anti-clockwise; a stiff old one may not be fully open.
A frozen pipe.
How to tell: a cold snap, and Thames Water's tip is a light coating of frost on the pipe. One outlet or the whole house can be affected depending on where the ice is.
The outside stop valve has been turned off.
How to tell: the inside stopcock is open, the house is dry, and a neighbour or a contractor has been working on a shared supply. WaterSafe notes that older homes and shared supplies may not even have their own outside valve.
A problem in your own plumbing.
How to tell: only some outlets are affected. No hot water but cold is fine points to the cylinder, tank or boiler, see no hot water but heating works. One tap or one shower points to a closed isolation valve, a blocked aerator or an airlock. A combi boiler will not make hot water at all if the cold mains pressure is too low.
A leak on your supply pipe.
How to tell: low pressure at every tap, a wet patch or greener grass in the garden, or a water meter that keeps moving with every tap off. Thames Water is clear that the supply pipe from the boundary into the house is the homeowner's.
Low mains pressure that is within the rules.
How to tell: the water has always been slow rather than suddenly slow. Water companies guarantee only 7 metres head, about 0.7 bar, at the boundary, and most aim for 10 metres, about 1 bar.
What can I safely check myself?
Everything here is done at the taps, the stopcock and the water meter.
- Cold kitchen tap. If it runs, the mains is fine and the fault is inside; if it does not, carry on down the list.
- Inside stopcock. It is usually under the kitchen sink, otherwise in a cupboard, a downstairs toilet, the garage, the cellar or under the stairs. Turn it gently anti-clockwise until it stops; WaterSafe's rule is to turn it slowly and never force it, because over-tightening damages it.
- Neighbours and the network. Ask next door, and check Thames Water's network page for your postcode. If the street is dry, report it to Thames Water, not a plumber.
- The bucket test, for low pressure. With every other tap and appliance off, the kitchen cold tap should fill a 4.5 litre bucket in 30 seconds. If it does, the pressure is what the supplier is required to provide.
- Frozen pipe. Turn the stopcock off, clockwise, open the cold taps, then warm the frozen section with a wrapped hot water bottle or warm towels, starting at the tap end. When water flows, run a dry cloth along the pipe to check for leaks before you turn the stopcock back on. Any wet patch is a plumber's job.
- Meter test, for a suspected leak. Turn every tap and appliance off, read the meter, wait 30 minutes and read it again. If it has moved, water is leaving your supply pipe somewhere.
- Isolation valves. Under a sink or behind a toilet, the small valve on the pipe has a slot or a lever; the valve is open when the slot or lever lines up with the pipe. If one has been turned across the pipe, turn it back with a screwdriver.
Do not force a valve, do not dig, and do not open the boiler.
When do I stop and call a plumber?
- If a leak is running near sockets, lights or the consumer unit, switch off at the main switch only if it is dry and safe to reach.
- Do not keep resetting a combi boiler that has locked out for lack of water, and if you smell gas, leave the property, do not switch anything on or off, and call the National Gas emergency line on 0800 111 999 from outside. Anything inside the boiler is work for a Gas Safe registered engineer.
- Stop if the stopcock will not turn or is stiff, if the outside stop valve is the one that is closed, or if a frozen pipe is leaking once thawed. WaterSafe says the outside valve belongs to the water supplier, you may need its permission to operate it even in an emergency, and you can be liable if you damage it; contact Thames Water rather than turning it yourself.
- A leak on your supply pipe is yours to repair, and Thames Water expects it fixed within four weeks; if you are on a meter you may then claim the cost of the lost water. Use a plumber on the WaterSafe register; they are trained in the Water Fittings Regulations that govern this work.
What does it cost in London?
A plumber in London charges £86 to £140 for the first hour on a weekday and £113 to £220 in the evening, at the weekend or at night, then £55 to £95 an hour. A seized stopcock or a closed isolation valve is hourly work, usually inside the first hour, plus the part. If the cause is a leak on the supply pipe, finding it is £150 to £300 for a basic survey and a repair behind a wall or under a floor is £180 to £300 or more; a pipe you can see is £120 to £200.