Boiler plumbing?

so I need to replace the presure reducing valve that feeds my boiler. The heating guy recommended this on our last tune up but wanted $400 for the task. I picked up the same exact valve for $55.

I can shut down the water coming into the house from the street with no problem.

But once I start removing the old Prv. Is the water from the house heating pipes going to come gushing back out the valve that I’m removing? Isn’t it under pressure also, like 12 lbs worth?

 

Yes, drain as much as you can at the lowest valve in the house, may be right there on the boiler, boiler drain. Use tephlon tape and pipe dope when reassembling. Is it, the prv, the exact same size as what you are replacing, are you going to need new nipples to make up the difference?

 

It’s the same exact prv. Take out the old and put in the new. Got the tape and pipe dope. I was just a little confused about the back pressure, once I start to remove the old. But I think you confirmed for me that I need to be aware of that. Thank you.

 

On the boiler itself, there should be a boiler drain you can attach a hose to, should be....

 

One more question. After I replace this will I need to purge the system?

 

Is there not a check valve or a back flow preventer on the line? Most systems are required to have one.

I'm wondering if you may have a combination pressure reducing valve/back flow preventer. This would explain the higher price.

I would love to see a picture.

 

should be a drain at the low point of boiler, valve what you can off and make sure you turn your auto fill valve off as well. you'll need to bleed radiators once filled or they will be airlocked

 

That’s correct, but I’m almost scared to turn that valve because it’s so corroded and my fear is it will start leaking also.

 

I’m getting a pic now, back in a sec

 

Should be the standard 1/2" fnpt FB-38 you will have to bleed you just introduced air into the system.

 

I'm a little confused.

You state your system pressure is 12 psi. That's a normal pressure. Thus This means that your PRV is operating correctly.

What am I missing?

 

It’s dripping, leaking.

 

Save some trouble.

Turn off boiler and circulation pumps, turn off city water to the system, lift boiler relief valve to take off the pressure. Change PRV. Very little air will enter the system. Should make it easier to bleed the system when done.

 

Wow you got a lot of rusty parts there. I would change the FB38, the nipple, tee and the short nipple above the expansion tank. you already taking it apart. do it one time do it right.

 

Perfect! That’s what I will do. That way I won’t need to open that old valve at the bottom of the boiler to release back pressure. Correct?

 

I've seen a lot worse.

I'm glad to see you have a union near that prv.

Do you have valves isolating the boiler from the piping to and from the house?

 

Yes I do. I will close them first to isolate as much as I can and keep them from getting air inside

 

Correct. Lifting the relief will drop the pressure. Just be aware that you have water in pipes going upstairs. If you can isolate the boiler, gravity won't drain the upstairs plumbing.

 

Yes, I will shut them off. Thank you!

 

Your system has an air scoop and an air elimination valve. Those things will help getting rid of the little bit of air you let in when you change the prv.