A shower that dribbles and a bath that takes twenty minutes to fill are common complaints in Streatham, where much of the housing is Victorian and Edwardian and still runs on its original supply pipe. The good news is that the cause is usually easy to narrow down with a bucket and a few minutes of checking. Here is how to work out where the problem lies and what it realistically takes to put right.
People say pressure when they often mean flow. Pressure is the force pushing water through the pipe, measured in bar. Flow is how much water actually arrives, measured in litres per minute. A house can have decent pressure at the main and still have poor flow because the pipe feeding it is too narrow or partly blocked.
Thames Water, which supplies Streatham, is required to deliver a minimum of roughly 1 bar at the boundary of your property, which is enough to lift water about 10 metres. That is a low bar, and it is measured at the boundary, not at your upstairs shower.
The terraces and semis off Streatham High Road, around Streatham Hill and down towards Streatham Vale were mostly built between the 1880s and the 1930s. Many still have a lead or galvanised iron supply pipe of about half an inch in diameter running from the pavement to the kitchen. After a century these pipes fur up inside, and the usable bore can be a fraction of what it was.
Shared supplies are another local feature. A single pipe often serves two or more houses in a terrace, so your flow drops when a neighbour runs a bath. Houses converted into flats suffer most, because one old pipe is now feeding three or four kitchens and bathrooms. Add a loft conversion with a bathroom on the second floor and the pressure left at the top of the house can be very thin, particularly on the higher ground towards Streatham Common and Crown Lane.
Before assuming the worst, check the cheap possibilities. A surprising number of call outs end with a half closed valve.
If the supply pipe is the culprit, replacing it with 25mm or 32mm blue plastic pipe is the lasting answer. For a typical Streatham terrace with a short front garden, expect somewhere in the region of £1,000 to £2,500 for the private section, depending on the length of the run, whether it can be moled under the ground instead of trenched, and how much flooring or paving has to come up. Thames Water has in the past replaced its side of a lead pipe free of charge when the homeowner replaces theirs, so it is worth asking what is currently on offer before work starts.
Where the incoming main is sound but pressure is still weak upstairs, a pump is an option. Regulations limit a pump connected directly to the mains to 12 litres per minute, and these typically cost £400 to £900 fitted. For more than that you need a break tank and booster set, or an accumulator, which usually runs from about £1,500 to £3,500 depending on size and where it can be housed.
Older gravity fed systems with a tank in the loft can often be improved by fitting a shower pump or by converting to an unvented cylinder, but the second only works well if the mains flow is good enough, generally 20 litres per minute or more. Test before you spend.
If your bucket test shows under 10 litres per minute with the stop taps fully open, or you know you have a lead or shared supply, get it looked at properly. A plumber can put a gauge on the main to read static and working pressure, which tells you in ten minutes whether the fault sits with the network, the supply pipe or the plumbing inside the house.
It is especially worth doing before a new bathroom, loft conversion or extension. Sorting the supply while floors are up and the front garden is already disturbed costs far less than going back to it afterwards.
Thames Water owns the main in the road and the pipe up to your property boundary, usually marked by the outside stop valve. The pipe from the boundary into the house is yours to maintain and replace, and on a shared supply that responsibility is split between the properties it serves.
It can be, as lead can dissolve into drinking water, which is a particular concern for young children and during pregnancy. Thames Water will test your water for lead on request, and replacing the pipe solves both the health risk and the poor flow.
Only if there is enough water arriving to pump. If a narrow or furred up supply pipe is restricting flow, a pump has little to work with and the pipe needs replacing first.
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