For those with a flatplate heat exchanger, the temperature of the water can reach 180 degrees. The shower control does not have much of an adjustment, making taking a shower a sometimes dangerous proposition. (I have scalded myself a couple of times.) What this modification does is add a tempering valve on the supply line. The tempering valve is an adjusting valve that mixes the untempered hot with cold, producing tempered water. The valve has an adjustable set-point anywhere from 120 to 160 degrees. By setting the valve at its coolest position (120) its much easier to use the shower's mixing valve to accurately provide just the right output temperature. I.e. you are only adjusting from 120 down, rather than 180 degrees down to say 100.
I purchased the valve at a plumbing supply store. (they are not available at the big box stores.) SMB uses PEX pipe and fittings, which is relatively new piping system. The problem with the PEX system is that you either have to use the PEX type fittings with a special crimping tool, or use the Sharkbite slip-on fittings. I made the decision to use the PEX fittings, as I had a number of 90 angles to make in a confined area. (The Sharkbite fittings take up a lot of room.) I tried the local tool rental yard, hoping to rent the crimping tool. The manager said he was expecting the request, but as of now, they didn't offer the tool to rent. I have heard that SMBW has one that they will lend to you. Home Depot carried them for $95. The come in 3/8", 1/2", and 3/4" sizes. There is also a tool that adjusts between the sizes but its cost is $150. Figuring I will need it again for another project, I opted to buy the 1/2" crimper.
Parts cost:
The valve is a Watts 70A, cost was $72 +tax.
Fittings & pipe $20.
Time 4 hours. (but this included 2 runs to the hardware store)
Complexity - Easy. Once you have the crimper, working with the PEX is real easy.
Valve, Crimping Tool and Fittings
The Before Shot
Valve on workbench ready to install
Ready to test
Look Mom, no leaks!
Ran the engine for 30 minutes to develop 180 degree water. The water at the sink is hot enough to make tea. At the shower I can just barely keep my hand in the stream. Its much easier to adjust the shower mixing valve to a comfortable temperature without using a gallon of water to test it with.
The valve came with a warning not to install it next to a fixture. Its meant to be installed right on a water heater. It's response time probably isn't fast enough to please the liability lawyers. But so far having it right in front of the shower seems to work fine. Another reason I went with the PEX crimping tool was to return the piping to the original condition if this didn't work out okay.
Linear Mode
