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Author Topic: Prv overflowing issue  (Read 1859 times)

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Offline mark3166

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Prv overflowing issue
« on: July 02, 2015, 08:56:24 PM »
Hi guys, just wanted to ask a quick question regarding a low pressure Hwc before I call back there tomorrow.
I called to this property a month ago due to their vent pipe overflowing on their roof, the prv was ancient so I suggested a new one. I installed a new nefa 3.7 prv and also extended the vent on the roof, once I turned the water back on and adjusted the valve till it overflowed, then I wound it back, I found that no matter how far I wound the spring back out I couldn't get the vent to stop overflowing. I thought maybe some debris had passed into the new valve, so I checked the prv washer and flushed it out, no sign of any debris. I then adjusted the valve again and wound it back once it overflowed, everything seemed fine.....until today.

I quickly called by on my way home today after being informed the vent was overflowing constantly again. I had a quick look and found it was overflowing, I decreased the pressure and found the valve seemed to only fully shut off once the adjustment screw was almost completely out of the prv (the vent is more than long enough), I wanted to ask on here as I've never had this issue before and I'm hoping it's something simple which I'm just not picking up on.

In summary,
Low pressure cylinder, 3in1 valve before prv, then 20mm gate valve on cylinder. No temp valve.

Any ideas would be great, thanks in advance

Linkback: https://www.plumbers.nz/plumbing/1/prv-overflowing-issue/1886/

Offline Enn

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Re: Prv overflowing issue
« Reply #1 on: July 03, 2015, 04:13:23 PM »
You might want to check for a cross connection, mixer taps and washing machines are likely. listen for water passing through the valve with a screw driver , put on end on the valve and your ear on the other.
turn off the washing machine at the wall and see if that makes a difference.
there is a possibility that the prv may be faulty.
best of luck.
''Never have so many been fooled by so few''
Plumbing is not a career it is a disease....

Offline Badger

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Re: Prv overflowing issue
« Reply #2 on: July 03, 2015, 04:36:10 PM »
I had one with a cross connection, a European couple had joined the two hoses (hot and cold) together, with a Y connection, bought locally apparently.... and hooked it up to the one cold supply to where the old washing machine was. It only happened randomly when the European washing machine called for both supplies, real random.

Try isolating and checking how each appliance is hooked up.

Or it could be "creep", never come across it personally but I remember it from talking to a PRV sales rep, which could be a point of contact for you.

Let us know how you go mate.
You can't choose who you are.....but you are the sum of your choices.......

Offline Badger

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Re: Prv overflowing issue
« Reply #3 on: July 03, 2015, 04:39:58 PM »
Sorry the two supplies were hooked together to one on the washing machine, they had taken the other one off the machine....good luck... its confusing just trying to write it....and its Friday

Offline robbo

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Re: Prv overflowing issue
« Reply #4 on: July 03, 2015, 04:43:52 PM »
hi guys, yeah had one similar where the client took off the rose of his `felton`mixer and put a ballvalve in, then rose into ballvalve to stop it dripping, took a while to find that but it cost him plenty,cheers

Offline bowtieboy

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Re: Prv overflowing issue
« Reply #5 on: July 03, 2015, 05:02:09 PM »
Could be a faulty pr valve, one thing to check is the washer in the cup, check that the indent from the jet seating on that washer is centralized, if it is not, that dedicates that the forks and main diaphragm  are pulling unequally down on the washer seat, i have seen this before with brand new nefa brand,
One other issue could be the jet is leaking, while you have the cap off, put your finger over the jet, crack the inlet valve and see if you have water leaking from around the base of the plastic jet.

As the guys have said check the rest of the house for a cross connection, usually a washing machine, but i had a house that was being renovated and the ensuite shower mixer was left on with a plug in the wing back for the slide shower ! 
good luck
I believe in doing a job once and right. !


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