Install Double Check valve

hal_sJuly 11, 2011

I have to install a double check valve assembly in a 3/4" horizontal copper line. The brass check valve assembly has 3/4" female pipe thread connections.

What is the best way to install this? Should I use a union on each side, or would compression fittings be better. The unit weighs about 5-6 lbs and its overal length is about 6" less than the length of the horizontal copper line that it will be installed in. The check-valve unit has its own service valves on each end.

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If you're concerned about heat and the new check valve, here's what I'd do...

put a sweat threaded 3/4" male end on one end of the destination pipes, go ahead and put check valve there, then cut about 10" of copper and put a threaded male end on one end then a 3/4" coupler on the other (and sweat those in) then screw your extension into the other side of the check valve and wrap a wet towel around the valve, then sweat the coupler end to the other end of the plumbing...

so something like...

----: (check valve) :----=-----

- : 3/4" copper
= : coupler
: threaded fittings

(I used something like this when I added a whole house filter... in that case the housing is nylon)

    Bookmark   July 11, 2011 at 10:39AM
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I'm not too concerned about heating damaging the valve, maybe more worried that the mass of the valve will soak up so much heat it would be hard to solder.
Also was thinking about if check-valve had to be removed or replaced in future, but I guess I can let someone else worry about that.

Third thing would be if there is enough "give" at the ends of the line to spread it apart and slip the assembly in. I think your method would solve this by using a coupling with no stops in it, use it as a repair coupling to slip over the joint.

I want the check assembly to be oriented "right side up".

    Bookmark   July 11, 2011 at 11:15AM
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An acetylene or MAPP gas torch will heat the fitting faster than propane, allowing you to complete the soldering before the valve gets excessively hot.
By loosening accessible clamps, I'm usually able to get enough play in a line to insert a stopped coupling.

    Bookmark   July 11, 2011 at 1:05PM
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The isolating valves should not both be directly connected to the check valve. The purpose of the isolating valves is to be able to turn the flow off from both directions to permit removing the check valve.

There should be an isolating valve on one end of the check valve, on the other end there should be a union and hopefully a short nipple to permit future size adjustments, then the second isolating valve.

Also, that assembly should not be supported solely by the pipe, it should have hangers to hold that weight.

    Bookmark   July 11, 2011 at 2:55PM
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