PRV leaking

I have a Burnham Series 2 boiler. The ITT Bell and Gossett reducing valve (B-38) is leaking very slightly at the galvanized pipe connection. If I drain the expansion tank and remove a little water from the boiler I will then be able to sweat the copper fitting to unscrew the PRV re-apply pipe dope, tighten the PRV and re-sweat the copper. My question is what do I do about the air that will be in the system. The water line goes into the PRV then branches to the boiler and above to the expansion tank.

Thanks for any help you can provide.

 

Do you have the B&G reducing valve and relief valve combination unit?

You should not have galvanized and copper piping together without having a dielectric union or (my preference) a brass fitting intervening. Also, since the PRV will definitely fail sometime it is best to have unions on both sides of the valve and (preferably) shut-off ball valves upstream and downstream of these unions.

As for the air that will enter the system...you will most likely need to manually bleed it.

 

The PRV is not a combination unit. Since the valve is brass I don't think I have a dielectric problem (copper->PRV->galvanized).

That's a good idea to put unions and appropriate shut-off valves while I have everything apart.

As far as the manual bleed do I just open all zone valves turn on the water and open the drain that is located near the bottom of the boiler. What about the expansion tank?

 

If you just drop the pressure to zero while insuring all valves (zone & otherwise) are closed, you probably won't loose much water. If you have copper between the PRV & the boiler, you can just cut it with a tubing cutter & quickly install a Shark Bite by male pipe thread with a valve screwed onto the male end. If you can't find Shark Bite fittings, a compression valve will do. The nice thing about either the Shark Bite or compression fittings are not having to have the water flow completely stopped unlike sweating a valve on. Either the Shark Bite or compression will also serve as a union.
Should you get any air, the auto-vents should take it out.

 

The Shark Bytes look like the way to go. How do I know if I have auto-vents?

 

The devices in this picture are all air vents. The ones with the small bottoms are for use on hot water systems. There are different sizes & may be brass color but most are of similar design.

http://taco-hvac.com/en/products/Air+Vents/products.html?current_category=87&PHPSESSID=c0e6b3726d9e848ca8ab83b856fe09c8

 

There are no auto-air vents on the system. It was installed in 1990. Should I install one while I have the system down? If so where if not what is the procedure for purging any air in the system. I have been doing a little research, and there are no vents at the registers (which seems to come up often). Sorry to drag this thread on so long.

 

I find it kind of unusual for a system installed that recently not to have any auto-vents, but so be it.
It really depends on the system design as to where & how many (if any) to install. Does your system have a device which looks something like this: (don't worry about color)
http://taco-hvac.com/en/products/Air+Scoops/products.html?current_category=123

Some pics of the boiler & piping would be a big help. You can post pictures on photobucket or other photo hosting web site & provide a link here. Once we see pictures, explaining how to purge the system will be a lot easier.
Don't worry about dragging out a thread, we are here to help & want to hear that you got it right.

 

No devices like that. The only thing close ia an antisiphon valve after the PRV.

Here is a link with 4 pictures that may help.

Again thanks for the attention to my problem (and my education).
http://s114.photobucket.com/albums/n277/fallfix/

 

Thanks for the pics. Big help. The reason you have no auto-vents or air scoop is you have a "conventional" expansion tank or more correctly called a compression tank. This tank does not have a bladder in it but uses air trapped at the top of the tank as a cushion. With this type of tank you don't want an air scoop or other automatic air removal devices because sooner or later they will remove the air from the tank.
From the looks of things, when you fix the leak, & turn the water back on SLOWLY, the air should go to the expansion tank, particularly if you drain the tank at least part of the way. Some people advocate regular draining of these tanks. I do not because when you do, you have to introduce fresh water. Fresh water is one of a boiler's worst enemies.

 

Thanks for all the help. This forum provides a great service for those willing, but lack the experience or knowledge to feel confortable with their efforts.

 

We are always glad to share our knowledge & experience with those willing & able to learn. Please let us know how things go with the repairs & if you have any other questions don't hesitate to ask. We have lots of good people in lots of different fields.