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Plumbing confusion: boiler backflow valve

budget76

budget76

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new house, still learning the new systems. Teach me please.

Wilkins 975xl valve probably 20 yrs old.

Backflow valve for nat gas boiler was dripping about a drop every 15-30 seconds recently so I decided to troubleshoot. Watched some videos, shut of the valves on either side and opened #1 check valve to inspect for stuck debris. Nothing much, flipped gasket to new surface for good measure. Reinstall and now instead of a drip full pressure water sprays out the bottom if I turn the feed back on. Doesn't matter if the output valve is open or closed this still happens

Opened the relief valve/diaphragm carefully and again nothing stood out, it's not supple rubber but no damage i could tell. Didn't open check valve 2 yet to avoid another variable

Am I missing something like a certain process to reintroduce the pressure and make the valves close or something? Not understanding why, but it seems like since I turned off the pressure the relief valve/diaphragm is now stuck fully in the open position? Even if #2 was stuck closed I can't see why that'd force the pressure out the overflow, if the thing works how i imagine it does


pic of valve. took this before i shut the water off.
1726835706547.png
 
M92PV4U said:
I would return the check valve like it was and check the diaphragm in the bottom piece with the 4 bolts for debris.
Click to expand...
both done. nothing obvious to me. I had the check valve in and out 4x to try to figure out what the hell i messed up with literally a plunger, spring and cap to reinstall.

the diaphragm rubber isn't supple like i suspect it should be. maybe it's just not moving right anymore and needs a rebuild? but why the hell did i go from a drip to a faucet makes no sense to me


I've rebuilt carbs. I'm not THAT much of an idiot around valves. but this scenario has me confused as hell


my belief: normal operation springs in #1,#2 compress and allow water to flow past valves to right. if pressure shuts off spring pushes valve closed so water can't flow left. water also flows into opening below #1 but relief valve is closed so nothing comes out. I guess I need to research why that relief valve opens to begin with / what the point of it is as I'm leaning towards that being my issue
1726838508097.png
 
oh, one more data point. I had to temporarily shut off the water to the house entirely because my washer valve was shit. The drip started after that. Could air in the line mess with the valve, and I just need to let it flow a little and let it bleed off or something? intuitively no but i have no idea
 
Chevy_man said:
Rebuild with new rubber pieces and go from there.

Rubber is one of those magical things that can work just fine while looking like garbage, or look perfectly fine and be complete garbage. :homer:
Click to expand...
Beat me to it.
 
i figured that's my next move. the only thing that makes sense is the diaphragm was holding on to dear life and warned me by dripping, but now it's too stiff to do its' job

found a good exploded view. i flipped the #1 and relief valve seal rings to the "new" side for good measure but neither looked bad anyway. and if they were nicked I'd expect a trickle, not a gusher of water

1726839322566.png
 
reading more.

i'm not sold its bad rubber. I think I need to figure out the right process order of opening valves / turning the water back on to make sure the relief valve gets the pressure to re-seal. Going to pop all 3 apart to check for any obstructions/free movement then grab an extra bucket or two and try this out before I replace any parts.

its not acting like a seal is leaking. its' like the relief valve is wide open which the below is telling me it's not getting the water pressure applied to the spring to close it

1726853758375.png


www.joshsgasandplumbing.com.au

Explaining backflow prevention - Josh's Gas & Plumbing

This article briefly describes backflow and the need for backflow testing
www.joshsgasandplumbing.com.au www.joshsgasandplumbing.com.au
 
more convincing myself its a valve opening/pressure initiation thing on the relief valve

this is feeding into the boiler which is not on, thus not demanding water. I'm applying pressure from the left. whether or not the RHS valve in my picture is open, it's hitting a wall versus flowing through #2 since the output area is full of either water or air

thinking if open a valve downstream near the boiler, open valve next to #2, then open the feed valve it may get me the pressure differential I need to close the relief valve up.

https://www.mrwa.com/PDF/Chapter23CrossConnections.pdf
1726854292346.png
 
There is a plastic seat in the bottom of each check valve, they screw in with a o ring seal.
Make sure they are not nicked or cracked and are tight. A thin piece of metal the right width will engage the notches and spin them in or out.
Also make sure the poppets slide easily inside the caps.
There is also smaller, third seat inside the relief valve same story.
Again make sure it slides easily in the bore of the rv cap and lube that o ring.
Don't mix up the springs in the check valve, one is stronger than the other.
IIRC the stronger spring goes in check #1.

To return to service: Both sov OFF , Turn on water supply , slightly open test cocks 2,3,4 ,
Slowly open #1 sov and close test cocks one by one as water starts to come out, this bleeds air.
Then open #1 sov all the way. Leave the device pressurized and use #2 sov to send water downstream as required.
 
SLiggwood said:
To return to service: Both sov OFF , Turn on water supply , slightly open test cocks 2,3,4 ,
Slowly open #1 sov and close test cocks one by one as water starts to come out, this bleeds air.
Then open #1 sov all the way. Leave the device pressurized and use #2 sov to send water downstream as required.
Click to expand...

thank you for this. I THINK this is my problem. i was just opening the #1 SOV (input) with air in the valve, couldn't find a procedure like that. I will give it a shot soon. my plan was to open the valve downstream, open #2 output valve, then slowly open input/#1 SOV to hopefully get the pressure to balance inside.


(in)conveniently I just found a bad shutoff valve for the Master bath toilet. so i'm going to fix that before I mess with the boiler check valve again - since I'm going to shutoff the whole house water feed for a couple minutes and that's when the drip started last time.
 
Tried the above. It's still sending the water out the overflow instead of past check valve #1. Installed a new overflow gasket assy with no change. Seat looks fine in all 3 spots no cracks

Wtf. The videos just turn the water back on. It definitely shouldn't be this hard
 
Figured then freaking thing out after fiddling for another hour then saying it made no sense, slowing down and figuring out how it actually worked. Then I found the little 1/8" water passage before check valve 1 and realized that's how the relief diaphragm gets pressured to push that seat closed

Grabbed the dust off can to blow the passage out and it was clogged with sediment. Some wire to clear it and good to go now


It's the stupid shit that wastes time. Now I know. Never dealt with one of these valves before. Didn't help it's up in the ceiling of the basement so visual was tough
 
closing this out with a picture that may help someone else in the future

circled water passage is what was plugged. so water was just free flowing through the dump/overflow/whatever in the red arrow path.

when water flows thru the small passage it pushes the big diaphragm/gasket to the right which compresses the spring and pushes the rubber seat to close the overflow.

1727367098446.png
 
:laughing::laughing: sorry but had to deal with that kind of crap all the time in our old facility. That stuff would always be plugged up to the point you could hardly tell there was a passage. It was aggravating beyond belief on a weekly basis.

And the rubbers can do weird things as well, like seal and once you induce air never seal again or not seal on the other side as it's got a groove or imprint molded into it.

Glad you got it fixed
 
Weasel said:
:laughing::laughing: sorry but had to deal with that kind of crap all the time in our old facility. That stuff would always be plugged up to the point you could hardly tell there was a passage. It was aggravating beyond belief on a weekly basis.

And the rubbers can do weird things as well, like seal and once you induce air never seal again or not seal on the other side as it's got a groove or imprint molded into it.

Glad you got it fixed
Click to expand...
i don't think i can count how many times I said "this makes no F-ing sense. i changed NOTHING":homer::laughing:

not upset, i learned something. just annoyed I wasted 2hrs of 'free" time figuring it out
 
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