Back flow drip

Grallert

For the past couple of week I've had a drip from one of our BF devices an LF 909. It recently passed inspection even though it has a drip. It seems that it only drips while or after we use water. The drip is from the relief. I went ahead and serviced it with new rubbers. It still drips. Is there anything I am missing or should look at further?

Thanks in advance.

hot_rod

If new seals and gaskets did not correct the drip, either a spec of debris is stuck in one of the checks, or the seat is damaged, nicked or a piece broken off.

There are two checks, but also seals at the relief port that need to be inspected.

It should not have passed if it was dripping when the inspector finished.

Intplm.

@Grallert You say you serviced it with" new rubbers" ? What rubbers are you referring to?

Debris can get caught in the device causing the drip, even after the thing had been tested. Often the debris can and should be flushed out and that can be done by removing the first check and turning the water on. Put your hand over the opening while the water is running adding some back pressure helping to flush that cavity.

Another thing to do is to flip the disc on the check (1st check) that is located on the stem and spring. Flipping it exposes a side that doesn't yet have exposure to water and the seat. Also check the stainless steel ring that is the seat. Feel for any disfigurement.

If that doesn't work the relief might have debris in it too. Flush that as well.

The watts 909 is one of the best BFP made and can very often be repaired successfully.

Grallert

I'm not sure if it was actively dripping during the inspection, I did mention it though.

The repair kit comes with all the O rings for the checks and relief as as well as the check disks. That's all been replaced so I'll hav3e a closer look at the interior and flush it out better. There most be a bit of junk in there on one of the seats.

hot_rod

Dirt happens! Especially when you start disturbing the piping. The sooner you correct it the better.

Grallert

I'll get it this afternoon. It happens to be in a very tight spot and if I gained two pounds I might get in but would need to be pulled out :) Unions would have been a nice addition to the install.

Mad Dog_2

Backflow devices, especially on hydronic boilers are notorious drippers. I've seen quite a few very legit outfits throw a 1/2" plug in the atmospheric port AFTER the inspection. Mad Dog

Grallert

I've lost count of the 1/2 plugs I've seen in 911 back flows. My 909 has stopped after the repairs. Oddly it took a day. My guess is the crud finally flushed through. But I'll keep an eye on it.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1851524#Comment_1851524

The dual check I have on my steam boiler drips from time to time. It seems to happen from pressure varying on the supply side of things. I guess it makes sense, if the system has 60 PSIG and then you drop the supply side down to 50, now there's 10+ above the supply on the boiler side since the valve is closed.

Intplm.

https://forum.heatinghelp.com/discussion/comment/1851525#Comment_1851525

Great to hear the thing stopped dripping. They can be a real pain in the neck. At times, BFP's will drip from the relief because it is sensing back flow and not because they are broken. Back flow of the water will cause a drip too or, even a full flow discharge. Residual water can show up for a while after the device has fully closed the discharge.

If this ever becomes a nuisance you can install an air gap and pipe it to a drain.

hot_rod

The most common cause of an occasional nuisance drip is caused by a water hammer. A fast closing solenoid valve causes a spike and droop and the BFD will spit for a second. It's doing its job!

Actually by design the rivits that hold the label on are drilled into the center chamber. Intended to keep that chamber from being pressurized.

I suppose they could corrode after time and stop seeping.

By code all BFD vents are supposed to be piped to the floor or a drain. That rarely happens :(

Grallert

Actually by design the rivits that hold the label on are drilled into the center chamber. Intended to keep that chamber from being pressurized.

This is interesting I had no idea.

We have two big mains that come onto campus and I think this started after some work on the city main.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1851560#Comment_1851560

mattmia2

should use pop rivets