Back flow preventer dripping?

Timco

Just installed a new Zurn 975 XL, double check. Brand new, and drips. The old unit was running solid from vent and owner opted for new. I installed a good house filter upstream and it already caught a lot of rust, but the new unit had the filter in place before it saw any water. BFP is protecting a 1 mil btu steamer with a solenoid makeup water setup. Suggestions? Boiler is off and BFP is still dripping. Boiler was not run since it was installed. I drained boiler to run BFP and filter a few cycles after install.



Thanks, Tim

icesailor

Dripping backflow:

I'm not really familiar with this backflow but is there pressure on the backflow on the street side? I've seen where installers install the backflow AFTER the fill valve and when you shut off the fill, they may leak. I would think that the solenoid should be after the fill valve and street pressure be always on at the backflow.



SWhat size is the backflow? They have repair kits for most of them. Though they can be a challenge to repair.

Timco

It goes....

Service valve, filter, BFP, y strainer, solenoid, boiler. Yes, there is city pressure to the BFP and I cycled it a few times to get the air out. It is 3/4" and I did quote a complete rebuild, vent, checks and seats. They chose new because someone else 'rebuilt' it last year and now it was a full stream of water, not just a drip. The union between the BFP and the solenoid does have the smallest drip, which I will replace Monday. Just barely wet.

icesailor

If it's anything

like a Watts, what a bear if it is 3/4". I have big fingers and hands and I couldn't for the life of me, get those disks in place.

I use "Super-Lube" synthetic grease when putting these things back together. It works great and doesn't cause Butyl Nitrate O-rings to swell. It is clear. It is the only grease I use now.

Sounds like you have some debris in the valve. Maybe dismantling it will solve it.

Timco

Dismantle

Hate to dig into new equipment when it had a filter installed from beginning. I am thinking the tiny release of pressure from the leak maybe? Sheeeesh....thing is brand new.

Mark Eatherton

Too much of a coincidence....

Tim, I think your back flow preventers are trying to tell you something. I suspect that they are seeing a condition, like a reduction in incoming pressure caused by solenoids or flushometers valves that causes it to see the drop in incoming pressure, and then it spills and spits. Either that, or an increase in pressure on the closed loop side, like when an expansion tank goes south...



If this is the case, it can generally be solved by installing a spring loaded check valve upstream of the BFP. THis way, it can't "see" the drop in pressure on the inlet and will quit doing its thing. If it continues, I would look at the expansion tank and make sure it is properly sized and correctly aired up.



ME

icesailor

Contact the MFR

and see about this problem. There may be something about your installation that is causing this. These valves can be difficult to DX.

If they ask you about the test device and have you used it, it may be something.

I do oil burners and there is a pump tester that you can buy that will tell you if the pump is failing and there is no other way to test the pump for this. Other than the trial and error method.

Timco

Boiler

Thanks for the ideas. It is a steamer that is being protected, and has not fired since installing the new BFP. I would agree that it seems to be a condition causing this, not the devise. Trouble is, no pressure on protected side to push back...just the 2 feet of pipe between solenoid and BFP. Even if the solenoid closure hammered the BFP and made it drip, that should be momentary and not continue for a day now. Really pricey devise to fail from box, and filtered from beginning. May end up looking for debris in it but acts like a condition issue.