Large leak from backflow preventer on gas water heating system

genericnj · July 2019

I have a gas fired baseboard hot water 2 zone system. Moved into this home a year ago had no issues during the heating season. Today I was installing floors in one of the bedrooms and may have nudged the baseboard pipes once or twice, but nothing hard, just tap here and there -- same as kids would do playing around ... At the same time I did have water turned off at the main since I have a well water filtration system in that bedroom closet and did not want to have issues with water as i moved some of the items around during the floor work. When I finished the floors, i turned the water back on and in my utility closet I heard water hitting the floor -- I peaked in and water was pouring out of the backflow preventer valve, which is located at the feed to the boiler. There is a water feed off valve ahead of the backflow preventer, which i turned off and it made the leak stop. The system is appx 30 years old and I am not sure whether anything has or has not been replaced during that time. What could have caused the sudden leak and what options do I have to stop it?

many thanks for your help!

hot_rod · July 2019

Yes, water hammer or hydraulic shock can cause a BFD to spit or leak. if it is 30 years old, I'd replace it. A water hammer arrester or swing check valve upstream can also help prevent occasional spit or dripping. Often times a spit is caused by the BFD doing what it is supposed to do

What is your incoming water pressure? Do you have a thermal expansion tank on the water heater?

Filtration equipment often have check valves so you may need to have a DHW expansion tank added.

If you heating system holds pressure, no leaks, many installers prefer to leave the fill valves turned off. I'd be sure the boiler has a working low water cutoff safety, properly installed.

Jamie Hall · July 2019

The check and pressure relief valves in backflow preventers can -- and do -- hang up. Which is why there is an outlet one can see, since if they are hung up, they aren't doing their job.

Best thing at that age is to replace it, particularly if it is really dripping -- never mind running -- and not just "spitting" a little.

On expansion tanks. This is well water? You have, of course, and expansion tank to control the well pump. At least I hope you do -- otherwise the pump is destined for a short and miserable life. You also have an expansion tank on the hot water heating system. Now. If there are any other check valves in the domestic water system between the water heater and the well pump control tank, you must have another expansion tank to account for the hot water expansion.

genericnj · July 2019

thank you both - in terms of water feed - there is a well expansion tank, which then feeds into a water radon system that depressurizes and stores water in another tank which is treated. This then feeds into a smaller expansion tank which is pressurized by a small pump and distributes water to the filtration system for sediment. The radon system controls the pressure for the whole house and is set to 50 psi as the filters post the radon system are rated to max efficiency at 50 psi. The hot water heater does not have an expansion tank, however as I live on my own, i leave it at Low and hot water only slightly raises the pressure (I have multiple meters along the line) when water is heated.

My biggest challenge is with how tight it is where the backflow preventer valve sits -- it is positioned in a small utility closet BEHIND the boiler in the very corner -- there is not enough room for even a bucket under it -- probably 2 inch of room around it as it is against a wall and pours water onto the wall ... not optimal setup, but since this is all in a small closet when they built the house they did what they could to fit it all in... When i was installning a new hot water heater, i had to dent the side of it to make it fit because of how tight it is in there ..

Any ideas on how to 'encourage' the valve to seal correctly? maybe some pressurized air into the vent side? I'm trying to think what I can do without disassembling half the boiler to get to that valve ...

Jamie Hall · July 2019

Gotta love it when people cram things in like that.

What make and model backflow preventer is this? It is remotely possible that you might be able to get the offending part of the valve to clear and seat properly if you could flow a large flow through the valve. Without seeing how your boiler piping is set up I'm not just sure how you could do that without really messing up your hot water heating system though.

I would presume all this is on copper pipe? You may find that the easiest thing to do -- assuming that you have other useful valves (which you may or may not have...) is to remove the backflow preventer entirely from where it is, and relocate a new one where you can get at it. I'd have to look at the space, though, to see if that would work -- or is even feasible.

hot_rod · July 2019

Also the vent port should be piped to a drain or at least an area that could handle occasional discharge. The valve will have a threaded port, or optional tundish to connect to.

Got a pic? Most are easily disassembled to service or clean out.

genericnj · July 2019

The discharge is aimed at the wall, i kid you not ... not piped anywhere good and this is in a living space so any discharged water goes straight onto wall and floor. I'm glad I caught it relatively quickly, there was quite a bit of water but not a full flooded room yet and hardwood floors seem to be ok.

Yes this is on a copper line -- replacing it with one higher up may be better, but a difficult job without taking apart much of the boiler's exhaust and expansion tank..

Here is a couple of photos to show how difficult to access and what valve it is.

On label it states BFP-90 by MDRCA Corp.

genericnj · July 2019

Quick comment , i just noticed the first photo is very misleading, the discharge pipe from the backflow preventer is NOT connected to the larger pipe coming out of the expansion tank -- it is aimed behind that pipe, just very close to it so appears to be connected in the photo.

hot_rod · July 2019

Well you may need to remove some flue piping to get good access.

Here is a cutaway of what is inside, the black lines are all sealing areas, one on each check and the spool in the center.

Installation and testing procedure, although you know it leaks

Some times you can disassemble and clean some crud out. The longer it leaks the more prone to seat damage which is not rebuildable.

Ideally the should be mounted in a horizontal line.

It has union connections, changeout should be fairly easy once you get to it.

HomerJSmith · July 2019

These double check with atmospheric vent are cheap, just replace it. Put a ball valve on the output of the valve so you can shut it off if need be to the boiler and not having to drain down the boiler. Fixing it is necessary if it is leaking, so bite the bullet and do it.

Like the expansion tank, that double check is old. I'd replace both. See: Supplyhouse.com

http://heatinghelp.com/blog/how-diaphragm-tanks-came-to-be/

hot_rod · July 2019

Pretty much everywhere you look at those older systems there is room to upgrade. It's hard to pick a stopping point.
Then again, some of the older versions of hydronic components will last longer than todays "value engineered" versions.

HomerJSmith · July 2019

Yes. You do a cost vs benefit analysis. If the cost of repair exceeds the cost of replacement, it's decision making time. Generally, the longer you keep a system going the more cost effective it is.

Intplm. · July 2019

@genericnj Replacing the BFP is the thing to do here.
If you have the room, move the BFP to a more easily serviceable place.
You probably have debris caught in the check valve portion of the BFP triggering the the darn thing to discharge.

That BFP is very serviceable if you can get to it. It comes apart relatively easy when in a serviceable place. So, if you can get at it, take it apart and clean it. After that it should seat nicely.

Considering its age and its current location however. I would replace it as mentioned above.

The debris more than likely got caught in the BFP because you turned the water main on to quickly?? Drawing water and rust from the other side of the main. Next time go very slow when opening the main valve.

Jamie Hall · July 2019

To several people's comments: may I add that that is a double check with vent, which is... ok... but not great. A reduced pressure zone true backflow preventer (more expensive) would be more reliable.

hot_rod · July 2019

Some installers are installing a fill tank system and getting away from BFD altogether.

Disconnect the fill and add a low water cutoff is an option. Probably a good portion of old fill valves are seized and would not work if they had to

BFDs like thermostatic mixers are valves that need occasional service to assure they are working correctly.

Keep pressure spikes and droops away from them so they don't have to "move" will keep them healthy longer.

genericnj · July 2019

thank you all for the advice and the diagrams. I did indeed turn the water back on pretty quickly and that indeed may have triggered the valve to move and get stuck partly open

I will likely just replace and maybe move it up the pipe a bit so it is more accessible in the future.

hot_rod · July 2019

A DC "double check" is another option, same function and look but without the atmospheric vent, so no leak on the floor potential. The downside is you don't know when they fail.

Inspectors is some areas consider them adequate protection for a boiler filled with plain tap water.

Start adding chemicals and glycols to the boiler water and you want a higher protection level.

If you are on a private well system, by yourself, the check is there to protect your potable water.

On a public water system the BFD protects everybody on the system and more and more cities are asking for RPZ , testable type that require documented yearly inspection and re-certifiction $$$.

If you replace it with a like product spend the time to run the vent to a location where discharge can be handled, a floor drain with and air gap ideally.

genericnj · July 2019

@hot_rod thx for the good advice -- in replacing unfortunately I will have no way to vent to a drain as this is in a closet in the living room and there are no drains in there nor room to create one. I will look into the DC valve option since I rather not have the problem of leaking which could have devastating results. Also I will be mostly keeping the feeder in off position moving forward and periodically checking to make sure the boiler is not losing water.

related question - in it's current state was there any potential the valve would be letting water out of my boiler and into my pottable water? for example if i turned off the water, so there is no pressure and then opened the taps with the feeder in the open position and the valve in its current partially open state?

Jamie Hall · July 2019

genericnj said:
...

related question - in it's current state was there any potential the valve would be letting water out of my boiler and into my pottable water? for example if i turned off the water, so there is no pressure and then opened the taps with the feeder in the open position and the valve in its current partially open state?

Very unlikely. That's why the vent is there. A Double check without the vent, quite likely -- which is why I never approved the use of double checks as backflow preventers. RPZ valves only, as @hot_rod mentioned.

hot_rod · July 2019

A number of failures would need to occur to allow flow backwards thru a DC or vented DC. Both checks would need to fail, a low pressure or back siphonage condition on the inlet side, no vent or a vent that has been plugged by an incompetent service person.

The labels on most are riveted on, and the holes are drilled thru to further prevent the center chamber from being pressurized, although not much of a flow path around the rivets, they will seep or spray to indicate a failure.

There are probably a dozen different types of back flow devices built and certified for various applications, the level of hazard and application determine which is best, as well as the local code enforcers.

I think you have a good plan, although I would add a LWC if you valve off the fill, for additional piece of mind, and code compliance. Most of the modern mod con boilers have pressure switched that lock out ignition if the boiler pressure drops indicating a possible low or no water condition. Flow switches are used on some applications, but a probe type LWC is really the best protection.

Yet another safety device to keep serviced and operating properly

Large leak from backflow preventer on gas water heating system

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