Why is my water pressure poor upstairs but fine downstairs?

The first thing to establish is which kind of system you have, because the same symptom is normal behaviour on one and a genuine fault on the other.

What you'll need

• A bucket of known volume and a timer
• Access to the loft and the stopcock

Step by step

1. Look in the loft.A cold water storage tank up there feeding the hot cylinder means a gravity system. No tanks at all means a combi or an unvented cylinder, both of which run at mains pressure.
2. Measure rather than judge.Time a known volume from an upstairs and a downstairs tap. It turns a vague impression into two numbers you can compare.
3. Understand gravity head.Pressure comes only from the height of water above the outlet. A bathroom tap two metres below the tank has about a fifth of a bar; the kitchen tap five metres below has more than twice that.
4. Check whether the cold is mains or tank fed.On many older houses the kitchen cold tap comes off the mains and everything else comes from the tank. That single difference explains most complaints.
5. Check the tank on a gravity system.Is it actually full? A partly closed ballvalve or a restricted supply leaves it low, which reduces the head to every upstairs outlet.
6. Check the stopcock on a mains system.A stopcock left part-closed after work is the most common cause of a house-wide pressure drop, and the effect is worst at the highest outlets.
7. Clean the aerators.The most common single-tap cause. Unscrew the nozzle and rinse the gauze; it takes two minutes and often solves it entirely.
8. Check the isolating valve at each poor outlet.A valve nudged part-closed under a basin gives exactly this symptom at that one fitting.
9. Consider the supply pipe on a mains system.An old lead or narrow-bore supply pipe from the street limits the whole house, and the effect shows first upstairs. Replacing it is a real job but it is the only cure.
10. Consider a pump or accumulator.On a gravity system, a pump. On a mains system where the supply is genuinely limited, an accumulator that stores mains water and releases it at a higher rate.
11. Do not pump a mains-pressure system.Combis and unvented cylinders must not be pumped. If yours is one of those, the answer is fixing the restriction or fitting an accumulator.

Tips

• Measure both floors before doing anything. The ratio between them tells you far more than either figure alone.
• Check the stopcock is fully open before anything else on a mains system. It is the commonest and cheapest cause.
• On a gravity system, raising the tank even a little makes a measurable difference to every upstairs outlet.

Common mistakes

• Expecting mains pressure from a gravity system — The pressure is set by the height of the tank above the tap and nothing else. No adjustment, cleaning or valve change will produce mains-like pressure from a two-metre head.
• Fitting a pump to a combi or unvented supply — Those systems are already at mains pressure. Pumping them is prohibited, risks damaging the appliance, and creates a backflow risk to the public supply.

If it doesn't work

Questions people ask