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We have a project fitting a backflow preventer (Watts 757) where none previously existed. Due to the tight space available, we would be cutting an existing pipe, and providing an elbow in order to gain some working space, and installing new pipe after the DCVA to an existing pipe end that currently has a grooved cap in place. Where we cut the pipe, I am anticipating welding a flange to the cut pipe to attach the new elbow with a grooved/flange adapter. The other pipe end created by the cut will require a cap. What is the best way to seal off this resultant stub? Is a welded flange the best way to attach to the existing pipe?  Thanks in advance.
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9 Comments
Anthony
9/6/2023 07:25:55 am
You could cut out the welded tee and groove the riser manifold put in a GxG filler piece. That'll give you more options I think. Welding in field is annoying in tight spaces like that.
Chad
9/6/2023 07:45:44 am
Agree 100%, cut out the tee, avoid any in field welding.
JJ
9/6/2023 08:05:59 am
I agree, welding in the field is not the best route. If needed, you could use a uni-flange and blind cap for the existing main.
Dan Wilder
9/6/2023 08:06:27 am
From a purely # of cuts/grooves standpoint and what I would suggest.
David Kendrick
9/6/2023 09:28:59 am
All materials prior to valve #1 of the backflow preventer should/shall be useable for potable water supplies. This could be cement lined ductile pipe and fittings, galvanized, Stainless, Copper or even plastic.
Dave
9/6/2023 10:46:09 am
I've done a lot of backflow retrofits and while your options are limited, I would do all I could to avoid cutting that stub coming throught the wall (is it S40?) Along with what David says above, one mistake and you are really screwed. Is there room to slide the riser manifild assembly over or raise it? Some galvanized grooved fittings are certified NSF/ANSI 61 but one has to check carefully. Is the stub through the wall properly restrained? The Ames/Watts/Deringer might be worth looking at.
kimberly olivas
9/6/2023 04:14:52 pm
I agree, cut out the welded tee, then you can groove that pipe and use the threads with a threaded companion flange on the piece going through the wall. there's a million ways to do, but welding in the field is not the best option, ever. 9/7/2023 08:20:40 am
An EBAA Iron, Inc. Series 2100 MegaFlange may work in this situation. They are UL and FM listed from 4" through 12". You would need to verify that the pipe you are installing the MegaFlange on is standard weight wall pipe (sch 40). The existing pipe probably is standard weight since it is threaded. Also you would need a "transition gasket" to adapt the MegaFlange to Iron Pipe Size. You can contact a sales engineer at EBAA to make sure this will work in your situation. We have found them to be good to work with.
Dave
9/7/2023 11:14:22 am
A couple general thoughts, if faced with similar situations (and granted, not having the full picture here), I still would not discount raising the riser manifold (if practicable) and extending pipe underneath, bringing the backflow into a position where it is serviceable, then loop around. Also verify that the pipe stands are sufficiently-sized per NFPA #13, the one in the photo looks small. And if installed vertical, make sure the backflow is listed in that orientation. Hydraulic calculations may have to be performed. Leave a Reply. |
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