What is Water Flow?
As we demonstrate with our Water Pressure Calculator, water flow is measured with a water flow meter but can be calculated in a simpler way if you do not have one. Put simply, it measures the litres per minute of water coming out of your tap. In other words, if you ran a tap (at full flow) for a minute, how many litres would come out? As we said in that article, ‘normal’ water pressure in UK homes is usually in the 10-15 litres per minute. When we use a water flow meter (more on that later), we are not measuring water pressure, that is different as we will explain below in more detail.
It can be important to understand how to measure water pressure and flow rate and understand water flow in and around a property, especially when you have a water leak as it can give an indication of how much water may be leaking into your property and how much it will cost for the water if you are on a meter. We explore that further in our Water Leak Calculator which is a very useful tool.
The greater amount of water that has leaked, the greater potential water damage.
Low Water Pressure / Flow – Water Leak?
Why is understanding water pressure and flow important? Well remember in our article about the Top 10 Signs of a Water Leak, number 9 on that list was low water pressure. Just like when you have pressure loss on a boiler, which is also a sign of a possible water leak. Why?
Well if you think about it, it is a bit like when you are having a bath or shower and someone flushes the toilet (annoyingly!), the flow of water slows down because some is being used elsewhere in the property. In a way, this simulates what it is like to have a water leak with water being lost elsewhere in your house. If you do have a water leak, do not ignore it and get help from a professional like us. We can help you find your leak with our water leak detection services.
Water Flow vs Water Pressure?
So we explained above what a water flow meter measures but how is that different to water pressure? To try and explain that simply, water pressure is the the amount of force exerted by the water in your pipes. A bit like when putting air in your tyre, the higher the pressure, the greater the amount of force the water is giving. It is a bit like you see with a pressure washer (the name gives it away!). Even though the flow of water is limited to the amount of water coming from the tap usually, the pressure washer forces it out of a small hole / nozzle at high pressure to clean with greater force than simply a hosepipe would.
Interestingly, water pressure is often measured using the same measures as you have when pumping up your tyres on your car, but more on that later on this page. Some water leak sensors work on detecting variances in water flow, which can help locate a leak between meter and house and quantify the amount of water too.
How to Measure Water Flow? – Weir Cup
As we mentioned earlier, you can use our water flow calculator to do this but another simple, inexpensive and relatively effective water flow meter is a ‘Water Flow Cup’ or ‘Weir Cup’ as they are sometimes know. You basically run your tap at full speed (normally) into the top of the cup.
The cup has a clever design that diverts and moves the water out of a gap in the side of the cup with a water flow meter scale showing litres per minute and gallons per minute. The top of the water level coming out shows the water flow. So in the image above, the flow is about 10-12 litres per minute which is fairly normal in the UK.
Useful Tip – you have to be slightly careful with taps with aerators (like the one above) on them as they make the water bubble a bit in the cup so try to ignore that element of bubbles. Ideally, if you can, use a ‘normal’ tap or one with the aerator removed from it. It will be simpler to read.
How to Measure Water Pressure? – Gauge
In order to measure water pressure rather than a water flow meter, you need a water pressure gauge such as the one shown above. Again, like the water flow meter, it is a relatively inexpensive device that attaches to your water system (usually to a threaded tap or washing machine style fitting).
As you can see in the image below on the left, once it is attached with the tap off, the gauge shows zero water pressure, which is correct when a tap is off! once you turn the tap on, very quickly it will rise to measure (see top right of the image above). In our example, the pressure is just over 50 PSI which is about 3.5 bar. Nowadays, PSI is a more common measure of water pressure than Bar.
Water Flow Meter – Demonstration
Earlier in this article we explained about how a Water Flow Meter Cup (or Weir Cup) is a simple way of measuring water flow. Well below is a video demonstration of one working. We also have a useful video on how to read a water meter on YouTube too – in a way a water meter reading (over time) can act as a water flow meter when you bring time into the equation to see how much water you use.
Thank you for reading our article and don’t forget to contact us if you need help with a water leak at your home. You may also be interested in our article about how to report a water leak which also explains who might be responsible for a water leak outside your home.
If you want to see another interesting videos, see our Slow Motion Water collection. Also, on a similar subject to above our article about how a pressure relief valve works. Finally, on the topic of water, if you are interested in water quality testing, see our guide to Water Test Kit Strip sampling and our subesquent report on Tap Drinking Water Tests
We hope you enjoyed our guide to water flow meters.
What to do if water pressure is low?
If you have a situation where water pressure is low in your house, it is important to understand why that is. Also, has it been low for a long time or is it a recent problem? Is it low in all of your property or just one part of it? It can be a good idea to speak to neighbours to see if it is a problem in the area or just your property. If you have low water pressure, it is possible in some instances that you have a water leak. Therefore, check for other signs of a water leak that might indicate that.
What is normal water flow for a house?
Water flow in houses may vary according to a number of factors, including the location and construction (including plumbing etc) for that particular home and area. That said, in the UK, normal water flow is likely to be between 10 to 15 litres per minute for most people. Water flow below 8 litres per minute would be considered very low and above 18 would be very high water flow. You can use water flow meters to measure this. Water flow meters come in various forms, or you can work it out yourself by running a tap for a minute and measuring the water flow.