What should the orientation of the inline strainer be?
By
Patrick Gordon, technical manager, Splashworks
SANS 10252 / 1 tells us to install a strainer, but the finer details are left to the manufacturers and installers to work out.
TECHNICAL 35
6.1.5 Strainers 6.1.5.1 A suitable strainer shall be provided to prevent the entry of solid particles of size exceeding 710μm into any fittings controlling water pressure or controlling the flow direction of water, unless such fittings incorporate their own strainers. Strainers for sizes 15mm to 25mm shall comply with SANS 1808-58.
Firstly, if the strainer has to protect the system from dirt, it stands to reason that the location has to be such that all the water to the installation passes through the strainer.
Next, it tells us that the strainer must be designed in such a way that it prevents any particles larger than 710 µ m into the system. Inside the strainer is a mesh that catches the dirt and prevents it from passing through. Particles of 710 µ m are equivalent to almost three-quarters of a millimetre – this is very large and the dirt that can get through is still large enough to damage the fitting downstream from it. Ideally, we want to get to a mesh size of approximately 250 µ m or smaller.
The downside of the smaller mesh size is that it now causes more restriction for the water to pass through, and we will lose some user comfort. Because of this, we need to look at the design of the strainer that we install and make sure that it not only has a fine mesh, but that it also has enough surface area to allow the passing of the water without much friction loss. The larger the surface area the less the effect of friction loss will be.
The next aspect that should be remembered is what the orientation of the strainer should be. This would be dependent on the particular design. If it is a‘ Y’ type strainer, as pictured below, you must make sure that the strainer is fitted as in the picture so that all the dirt is deposited into the lowest part of the fitting and that when the inspection cap is removed all the dirt is expelled to the outside and does not fall back into the strainer body. Also make sure that you adhere to the flow direction as indicated by the arrow on the body of the strainer.
Supplied by Google Images
Supplied by Google Images
The other type of strainer is a bowl type strainer. This type of strainer is installed on a horizontal line to facilitate easier maintenance. To service the strainer the bowl is removed and rinsed out. The strainer cartridge can normally also be removed for maintenance purposes.
Once again, the flow direction is indicated on the body of the valve, and it is of the utmost importance that this is adhered to.
I experienced a malfunction on my heat pump at home some time ago due to insufficient water flow. Fortunately, I have a strainer fitted and all I had to do was to clean the strainer and everything started working perfectly again.
A small item like an inline strainer can really make the difference in the lifespan of our installations.
It amazes me that homeowners will spend thousands on filtration for their irrigation systems, for example, but will gripe about fitting it to the supply for the house. PA
Need help or advice? For professional guidance or assistance with your system design, feel free to contact: Patrick Gordon | 083 303 1437 | patrickg @ splashworks. co. za
Do you have a technical question? Please email your technical questions to megan @ interactmedia. co. za, with the subject line‘ technical question’.
Supplied by Advanced Valves Supplied by Advanced Valves
March 2026 Volume 32 I Number 01 www. plumbingafrica. co. za