Back flow preventer: slow drip with system shut down


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Old 06-15-24, 09:00 AM
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Smile Back flow preventer: slow drip with system shut down

Hello, I have read a posting from 2004 on a very similar problem. I understand that by design, backflow preventers drip due to low pressure, but I wonder about the source of the water, so here are some specifics:

My hot water (boiler) system is shut down for the summer (using two ball valves on both the inlet and outlet sides of the backflow preventer), but I noticed slow dripping through the drain pipe connected to the backflow preventer. There is not connection to a floor drain. It might have been like this for some time, but we only noticed it this year as more water started to come out very slowly, dripping. The line from the main supply to the heating system includes the following (from the left to right on the photo)

From the left on the photo: MAIN SUPPLY/METER ---> FIRST BALL VALVE (WATTS FBV-1 REGULATOR)
/SHUT OFF WATER TO HEATING ---> BACKFLOW PREVENTER (WATTS 9D-M3) ---> PRESSURE REDUCING VALVE (ITT BELL & GOSSETT FB-38) ---> SECOND BALL VALVE (GIACOMINI R250D) shown on the lower right side of the photo --> PUMP.


With both ball valves shut off, there should not be any water flowing through the preventer. Yet, it fills up a 48 oz/3 lb) container within a week: Where is all this water coming from? I have attached the photo (below). The tree is not part of the heating system... Thank you in advance for any insights or experiences you can share. Have a great day/weekend!

Arjun


 
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Old 06-15-24, 09:04 AM
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I don't know anything about your particular valve but most valves need periodic maintenance... disassembly, inspection, cleaning, lubrication... possibly replacement of parts. I would suspect that if you did that, you might clean out a bit of sand or something that is causing your leak. Or if it still leaks after is is cleaned and lubed, you need new parts for it.
 
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Old 06-15-24, 11:56 AM
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It's completely normal for the PRV to drip when not pressurized.
The PRV is not your problem.
The ball valve feeding the PRV is at fault.
 
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Old 06-17-24, 08:02 AM
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Thanks, XSleeper.

We have had maintenance done on the system but not more recently. Obviously, we need to have them pay attention to this issue.

Arjun
 
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Old 06-17-24, 08:09 AM
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Thanks, PJMax/Pete.

I have tested the valve you referred to when I shut of the water to all things using water (boiler, toilets, and fridge), and the water meter stayed the same (it's digital). I was wondering if the second one between the PRV and the boiler might be letting water backwards due to gravity. Was that the one you were referring to? During the months we had the system on, there was no leak. Thanks!

Arjun
 
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Old 06-17-24, 01:52 PM
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It's possible you may be getting water back from the system.
Leave the system pressurized and turn the valves off.
 
 

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