2nd Backflow Preventer Leak - is this common?

jlonj

I'm trying to figure out if I just have bad luck with these things, or if it's a symptom of another problem.

I had an issue last year where my steam boiler started slowly gaining water. I have a manual fill. The backflow preventer then started leaking a few weeks later. My theory was the the manual fill ball valve was leaking and causing everything, but my new plumber (old one went out of business) was skeptical. The plumber replaced the preventer, but when the boiler still kept gaining water, he also replaced the manual fill a few weeks later. Since then, the boiler stopped gaining water, but this was towards the end of the heating season early this year.

Now, I'm having my boiler serviced, and the new backflow preventer started leaking right after the servicing. In the process of replacing it too.

I'm trying to figure out if these are just 1) crappy backflow preventers, if i have 2) crappy manual fill ball valves (i guess we'll see after this preventer is replaced), or 3) there is some other issue - does my boiler have something wrong that's causing pressure differentials in the water line.

hot_rod

Usually if multiple BFDs leak there is something causing it
one common cause is pressure spikes caused by fast closing valves. Solenoid valves for example.
if you have high water pressure it makes it worse. A couple suggestions, add a water hammer arrestor 
 Or sometimes a swing check upstream of the VFD to take the hit from a pressure spike.
unless it is corroded or a ripped seal, the drip indicates it is doing its job😉

ChrisJ

Are you on well water?
Any filters, or strainers?

Ever find debris / specs in your aerators on faucets?

STEVEusaPA

If you manually feed, why not put and close ball valves upstream of BFP and a second one between the BFP & the water feed.

ethicalpaul

STEVEusaPA said:

If you manually feed, why not put and close ball valves upstream of BFP and a second one between the BFP & the water feed.

I did just that. I'm glad it wasn't a crazy idea. That vent port on the BFP made me nervous!

ChrisJ

ethicalpaul said:

STEVEusaPA said:

If you manually feed, why not put and close ball valves upstream of BFP and a second one between the BFP & the water feed.

I did just that. I'm glad it wasn't a crazy idea. That vent port on the BFP made me nervous!

Mine is wide open over my head in the basement.

JUGHNE

I wonder if a full flow of water thru them would clean the sediment out from under the seat.
If they are passing water from just a leaky valve then not much flushing action going on there.
A full port bypass would pass a lot of water. You could even put a boiler drain below the BFP.

hot_rod

Depending on what model you have they usually have a screen on the input side. Some installers trash the screen as it slows flow when it plugs. Excessive teflon tape is one culprit.

By code, that vent port should be piped to an indirect drain, floor drain, or within a few inches of the floor.

In this type of BFD, three main seals that cause leaking, both concial checks, and on the center cylinder that closes off the drain port as soon as pressure is applied. They disassemble easily and can often be cleaned and put back into service.

ChrisJ

hot_rod said:

Depending on what model you have they usually have a screen on the input side. Some installers trash the screen as it slows flow when it plugs. Excessive teflon tape is one culprit. By code, that vent port should be piped to an indirect drain, floor drain, or within a few inches of the floor. In this type of BFD, three main seals that cause leaking, both concial checks, and on the center cylinder that closes off the drain port as soon as pressure is applied. They disassemble easily and can often be cleaned and put back into service.

Depends on the area.

I specifically asked the inspector and he okd mine as well as in person.

Should I plumb it somewhere?  Probably, but I haven't in 10 years.

clammy

I have always installed a ball valve after bfp and had the home owner use that to fill boiler . I have found that they last longer having pressure on then those that see no pressure till feeding water that s when they usually leak . I also do see what the house water pressure is and it extremely high I ll add a prv no sense in exposing a auto feed to excess water pressure . Some towns have hi water pressure where I live it’s not uncommon to have over 150 to 180 psi durning the nite . Peace and good luck clammy