24 Sep 2018
Posted by BP Journal Question: I am working on a 2” Watts model 709 assembly. The unit has failed the test and I want to replace the rubber parts. Can you tell me about this model and what to expect when I repair this unit?
Mark:
The Watts model 709 is a double check valve assembly. The ¾” thru 2” sizes of the 709 started production in 1979 and were discontinued in 1993. Early versions of this model utilized a bronze body and came standard with gate valves. Later versions utilized ball valves as shut off valves. No special tools are needed to change the rubber parts on this assembly.
Doug:
Each check valve cover is o-ring sealed and secured by four slotted screws. There is no spring load on the cover when removing the screws. The 2” 709 is designed with a check assembly that is attached to the cover and the spring is contained. To remove, simply pull the cover straight out of the body and be sure not to twist the cover. Twisting the cover can unload the spring prematurely.
Mark:
Once the access cover is off, the check valve components are exposed. The check valve is attached to the cover with a bayonet locking system. The check valve is spring loaded. To disassemble, carefully hold the cover and seat in both hands while pushing down and rotating the seat or (cage) ¼ turn. This will unlock the seat and the spring, freeing the disc holder.
Doug:
At this point the white plastic seat or “cage” can be inspected for damage. The check valve disc is sold as part of the brass disc holder and must be replaced as one piece. Reassemble the check valve in reverse order and make sure the seat o-ring is lubricated properly before reinstalling into the body.
Authors |
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 Mark Inman |
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 Doug Taylor |
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