Sprinkler Pressure and flow tests (5min read)

Pressure and flow tests are vital for installing fire sprinkler systems. This guide is for use by competent workers only. Please contact us to arrange a test.

What do the regulations say about pressure and flow tests?

Sprinkler systems in dwellings in the UK are regulated by BS 9251: 2021, which require work to be carried out by competent professionals. This is why we always verify any measurements sent to us by clients.

The standard also details the equipment to be used for the pressure and flow test itself, as shown in the image below.

What equipment should be used?

Proper equipment ensures accurate measurements. As firas accredited installers, we’re required to use the following equipment.

Pressure measurement

A pressure gauge, which has been calibrated within the last 12 months, and is filled with glycerin for a more stable readout. Suitable models are available from Sale Engineering.

Measuring flow

Flow should be tested using a specialist device, such as an F-1000 flow meter, available from Rapidrop. If you don’t have access to a flow meter, a rough approximation can be calculated by recording how long it takes to fill a bucket. So, if it takes 15 seconds to fill a 15 litre bucket, you’re running on around 60 litres per minute.

The test should be taken from just downstream of the stop tap, rather than at your kitchen sink. The difference in pipe sizes will affect the results.

How to take a pressure and flow test

A typical test will follow the steps below. The test should be taken during a period of peak demand for the local area (typically between 5pm and 7pm):

Connect the test rig to the system test and drain valve.
Connect a sufficient length of drain hose of at least equal internal bore to the end of the test rig, with the open end run to a suitable surface drain or receptacle. Ensure that the hose is as straight and level as practicably possible to minimize frictional losses. Do not submerge the open end of the drainpipe.
Close the stop valve (see Figure E.1) and slightly open the test and drain valve until pressure stabilizes in the flow test assembly, then fully open the test and drain valve.
Slowly open the stop valve until the design requirement flow is registered on the flow meter OR the design requirement pressure is registered on the calibrated pressure gauge.
Take readings from the flow meter and calibrated pressure gauge and check that they both meet or exceed the design requirements of the system. If so, the water supply is deemed to be adequate.
The test should be repeated for each design requirement.

In practice, it is often prudent to take measurements by opening the tap to 25%, 50%, 75%, and 100% to produce a curve for the design process. We always verify the results prior to commissioning in any case.