Water pressure and flow – what does it mean?
Water pressure is simply how we measure the force of water that gets through from the mains into the pipes in your home. We measure it in “bars”.
All you need to know is that the force needed to push water to a height of 10 metres is a bar. Flow is the quantity of water that comes out of your tap when you open it.
Pressure is constant from the mains, flow changes depending on the quality of your taps, the size of their aperture, the pipe sizing under the floor and any filters in place. Both flow and pressure are affected if multiple taps or outlets in the house are in use at once.
Why is water pressure and flow important?
Sometimes water pressure and flow in your home is just not up to scratch. While your local water authority has to provide you with a certain minimum amount of pressure, is that always really enough for a refreshing shower in this heat? Here, we explore what the main causes of low water pressure are and what you can do about it. So many homes in the UK now use combi boilers and these are connected directly to the mains water supply, they don’t use storage tanks or pumps. That’s why sometimes when you’re showering and someone else opens a tap you notice that your water flow drops.
How to test water flow
To test your water flow:
- – Take a measuring jug (about 1-2 litres in size)
- – Put it under the tap you’re testing
- – Time how long it takes to fill the jug.
Ideally, a 1 litre measuring jug should fill up in about 7 seconds – anything less than that indicates that there may be a problem and you should call your plumber to investigate it. 9-10 litres /minute of flow from your mains cold tap is good. 15-20+ litres/ minute is great and not uncommon in many properties.
Source: Water Pressure Problems
Credit: Salamander Pumps
Water pressure and your boiler
Check with your heating engineer for advice before installing a combi as some of them may not work below a particular pressure level. Your combi boiler should be sized to fit the flow rate you have.
Some causes of low water pressure:
– Increased demand in your neighbourhood (e.g in the mornings and evenings when everyone is showering)
– Poor plumbing (e.g leaking water mains, blocked service pipes etc)
– Larger houses with multiple bathrooms in use at the same time
Fixing Low Water Pressure
If your water flow is too low, call a plumber to check that there is no problem with your pipes. They will be able to measure pressure and flow rates and work out if the problem is peculiar to your property or your local area. If they can’t find the issue, the problem might be external. There may be long term work going on in the street, and so on. In that case you should contact your local water authority. For South West London, that would be Thames Water.