Basic Maintenance for a Symmons Mixing Valve (7-500B Symmons TempControl TMV)

A thermostatic mixing valve, also known as a TMV, is a critical plumbing part with a vital yet thankless job, and one that is thought of little unless it is improperly functioning or needs to be replaced.

Some TMV manufacturers, like Symmons, produce high-quality, reputable, and reliable TMV assemblies, some of them sold assembled and in cabinets, like the 7-500B TempControl assembly, which are built using high-quality components, are corrosion-resistant, and easy to maintain.

That said, these Symmons mixing valves still need periodic attention. Here’s what you need to know.

Why TMV Maintenance Is Important

Just in case you are not familiar with the operation of a TMV, it is a valve that tempers and mixes the hot and cold water streams upstream of the point of use. They are critical pieces of plumbing infrastructure that help prevent scalds and other injuries at the point of use, in sinks and showers.

Routine maintenance, including regular inspection and, where necessary, cartridge replacement, helps prevent these occurrences and keep your TMV in top working order.

The Basics of TMV Maintenance

The Symmons mixing valves in question are easy to maintain.

One of the most important aspects of operation is to ensure that the valve control mechanism is free of dirt, sediment, and scale. This requires an inspection thirty days after installation (and it’s a good idea to routinely inspect after that).

If it is determined that your water supply results in an accumulation of foreign material into the valve control mechanism, it must be cleaned monthly by removing the cartridge and soaking it in a de-liming or de-scaling agent. White vinegar will work in a pinch.

After soaking, wash off the deposits and ensure that the piston of the valve control assembly moves freely before replacing it.

Check valve maintenance is also critical to the proper operation of these Symmons mixing valves. If the check valves are obstructed by sediment or other foreign material in the water, they can allow water to bypass them into the other line, and the TMV will not properly temper the water. Remove and clean the check valve seats from time to time, as with the valve cartridge.

Another best practice, to prevent interruptions in use, is to keep a replacement cartridge for the system on hand, as replacement is easy.

To replace a cartridge, shut off the water supplies at the stop checks and remove the 4 bolts on the cartridge bolt flange, then pry off the bolt flange and pull out the cartridge.

At this point, either clean the cartridge and replace it, or prepare a new cartridge for replacement by greasing and replacing the sleeve O-rings.

Then, install the new cartridge, pressing it into place until the bolt flange is firmly seated against the housing gasket. Hold the cartridge in place, replace the bolts, and then tighten them.

Re-open the check stops and then set the temperature appropriately.

If these Symmons mixing valves are installed in a location in which they are used seasonally, at the end of each season, the cartridge should be removed and fully drained in order to prevent frost damage.

Need New Parts for a Symmons Mixing Valve?

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