Two pressure valves in my hot water system

[RichC1524]

Hello
I have a gas hot water heater tank. From the tank’s cold water intake pipe, I have an offshoot pipe sending cold water to my gas boiler. Within that pipe that leads to the boiler is a pipe leading down toward the floor , and it is an open pipe, just like you see when looking at the hot water tank’s t&p pipe that leads to the floor.
That second pipe that leads toward the floor (not the tank’s t&p pipe) is leaking, maybe 4-8 ounces a day. The leak just started very recently.
I have an expansion tank connected to the boiler but none connected to my tank. So, my question is this—what exactly is that second “pressure” pipe (the one that is leaking and is connected to the cold water intake pipe that leads to my boiler)
I can’t find a system that has one on any videos I’ve watched regarding hot water tank installations.

 

[voletl]

Post a picture

 

[Diehard]

Well if it's cold water to your boiler, it's probably the Backflow Preventer(Dual Check Valve with Intermediate Atmospheric Vent). And that would be the vent pipe dropping down which spits water for one reason or another. Sometimes because it's doing what it was designed to do and others because it may have gotten fouled up a bit and/or it senses a slight water hammer and/or differential pressure. Probably looks something like that that Watts 9D, in the attached file.

First off, make sure your boiler pressure isn't rising too high when operating. That could be a sign of waterlogged expansion tank and one possible cause of backflow preventer spitting.
Or high pressure could also be a PRV(pressure reducing valve) problem.

If none of these, the backflow preventer may need to be rebuilt or replaced. Probably easier to replace it.

 

[RichC1524]

Thank you Diehard. I took a closer look and it is exactly what you stated- a BFP (Cash Acme). I attached a picture. As you can see , there is a copper pipe running from the BFP down near the tank, and it is dripping out the bottom of that pipe. I just had my tank replaced last week, so I will have the plumber come back and check everything.

 

[Diehard]

It really doesn't have anything to do with the domestic water heater. It just happens to be located off that common cold water line, which feeds both the water heater and he boiler.
I don't know what if anything the plumber did with that unit but even if it wasn't touched during the water heater replacement, there's always the possibility that some crap found it's way into it.
It is a big coincidence. Maybe get the plumbing to flush it out. That may do the trick.

 

[RichC1524]

Will do. Thank you so much for the info. I’ve learned more about my hot water and home heat in this past week then I have in 25 years of home ownership.

 

[voletl]

You should have the plumber come back and ask him why the flue for your water heater is back pitched so much that even cutting the elbow didnt fix it.... And why he didnt get the correct size water heater to make it work.

 

[Diehard]

You should have the plumber come back and ask him why the flue for your water heater is back pitched so much that even cutting the elbow didnt fix it.... And why he didnt get the correct size water heater to make it work.

Good eyes! Looks like he even cut the stack 90 a bit to lower it.

 

[Diehard]

Will do. Thank you so much for the info. I’ve learned more about my hot water and home heat in this past week then I have in 25 years of home ownership.

Well that's where I have you. I've been a home owner for 50 years.

 

[RichC1524]

You should have the plumber come back and ask him why the flue for your water heater is back pitched so much that even cutting the elbow didnt fix it.... And why he didnt get the correct size water heater to make it work.

Yes, I see what you mean. The venting tube actually has a slight downward slope leading to my chimney. Also, as I mentioned, I have an expansion tank connected to my boiler - do I need to add one to my hot water tank??

 

[Diehard]

An expansion tank is typically used on a closed system where the water has nowhere to expand to. Always required on boilers.
Only required on water heaters if the water cannot expand back to the city water supply. Typically the case when there's a backflow preventer or a pressure reducing valve on the water service. If it was required and you didn't have one, you would have been having trouble with it over pressurizing and spitting water out of the Pressure & temperature relief valve. Also, I'm sure the plumbing would have said something.

 

[RichC1524]

Thank you Diehard.