[jebbard]

My furnace (boiler) has a small drip coming from the soldered downtube of the backflow preventer valve. It drips about one drop every couple of minutes. The main line runs through the backflow preventer valve. The heat in my home has been fine (baseboard water). Is this something that I should immediately address or is the bucket catching the dripping water adequate for now.

Thanks,

Jim B

[skiberger]

You should have an automatic water fill before the backflow preventor on the domestic line to the boiler. The boiler my have called for water and you may have sediment making the valve not seat properly. You could flush it by lifting the little lever on the fill valve to flush it out. Do it quickly, you don't want to overfill the boiler. May want to wait to also see what labman says.

[jebbard]

I know just what you mean. I will try it. Thanks.

[labman]

If that doesn't work, post back with some more details. Is the water coming out an open end or a soldered joint? Does the system have an expansion tank?

[jebbard]

The manual filler valve didn't work... still dripping. The backflow preventer valve has an opening in the bottom to which a 24 inch 1/2 inch open pipe has been soldered. It is dripping out of the bottom of the pipe. I don't know why the backflow preventer would have an opening in it unless for some type of pressure relief if it became clogged or something. I probably should replace it. Is it as simple as turning off the water, draining the furnace, unscrewing the two bolts and bolting on a new one with some teflon tape? That looks to be the current set up. The system does have an expansion tank but I replaced it about 2 years ago. How important is the backflow preventer to a furnace?

[labman]

Furnaces and hot water tanks got along great for years and years without backflow preventers. Recently regulators have pushed for them to make sure water doesn't flow back into the city supply lines and contaminate things. Run cold water into a hot water heater or boiler, and don't leave anywhere for water to go as it heats and expands, and something is going to give. Took old Tom in plumbing and I a while to figure out these new fangled back flow preventers required an expansion tank. If the water beyond the backflow preventer is heated and doesn't have a place to expand to, it will come out the pressure relief. Is the make up valve which is closed most of time, between the leak and the expansion tank? That is the problem.

[jebbard]

The way my set up is starts with the main line going into the back flow preventer... next in line is the manual filler valve then the expansion tank.

[skiberger]

The back flow preventor has that pipe if the boiler backflows, the water drains at the floor (saftey) instead of going back into the domestic system. That soldered pipe unscrews from the BFP. If you plan on changing the BFP, you should have a water shut off valve on the domestic line before the BFP and before & after the expansion tank. These are isolation valves so you don't have to drain the boiler to do repairs. The BFP's do just screw off for replacement. You shouldn't have to drain the boiler. The water fill will stop the water from "backflowing". If not, you'd have more than a drip.

[jebbard]

Thanks for the info.

Jebbard