Tempering valve
By Herman Strauss , Omega Test House
Much has been said about the importance of tempering valves lately .
TECHNICAL 35
Various tempering valves are available in the market , but the plumber / consumer has no way to compare the different valves and to know if all valves are fit for purpose or no + t . Other than information published by the suppliers themselves , no accredited third-party verifications are available .
One of the challenges in a plumbing installation is to balance the various risks . To protect the system from bacterial growth , and specifically legionnaires disease , it is important to store water at temperatures of at least 60 ° C . The use of solar water heaters continues to expand and many of these systems can generate water that is significantly hotter . This in turn poses a serious risk to the user and especially to vulnerable users that might sustain serious and even fatal scalding . It is so sad to read news reports on deaths caused by scalding – knowing that such deaths could have been avoided if only a tempering valve was used .
The importance of these valves was highlighted in the early 2010s at the height of the solar water heater rebate programs . At that time , the South African Bureau of Standards ( SABS ) identified the need to compile a local standard for these valves aligned with local challenges . Unfortunately , the first publication of the standard unintentionally included conflicting and ambiguous requirements to the extent that no product could be tested to the standard . The technical committee proceeded to review the standard to resolve the challenges .
Without trying to analyse the reasons why , it was unfortunately noted that no test facility in the country equipped themselves to test these valves and thus all valves supplied to the market remained untested to this SANS standard .
Omega Test House identified the need for these tests to be made available and equipped the test house with the required test equipment . We further proceeded to subject our test equipment and procedures to the scrutiny of the South African National Accreditation Scheme ( SANAS ), and we passed this with flying colours .
Today Omega Test House is the only test laboratory accredited to test tempering valves to SANS 1299 .
The question remains as to what benefit there is in testing , and if testing a valve does provide any information that cannot be verified during a normal installation ? The answer to that is , a tempering valve is not only tested to be functional under normal use conditions , but also to confirm the level of protection that it offers the user when things go wrong .
A simple explanation of how a tempering valve works , is that the functional components are set to continually mix hot and cold water so that the water existing in the valve will consistently be at a predetermined temperature .
The normal functionality is tested by connecting hot and cold water to the valve and measuring the temperature of the water released . A variety of conditions are simulated . Different hot water temperatures are used . The tests are also performed at different flow rates to ensure that the valve will remain functional under all conditions that it could experience .
The valves are further subjected to durability tests . The durability test generates conditions that force the valve components to respond to temperatures and to open and close at least 20 000 times . Thereafter the valve is again tested to confirm that it still functions accurately . The valve is also tested to establish what happens when the cold water to the valve is removed . There are various scenarios that can cause this exact condition or variations of this condition . The tests are designed to confirm that the valve will , in this case , not allow scalding water through the valve . The time it takes for the valve to close is an important part of these tests . PA
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All images supplied by SYR
“.. the level of protection that it offers the user when things go wrong .”
1 - 3 : Tempering valves
May 2023 Volume 29 I Number 3 www . plumbingafrica . co . za