Hydronic expansion tank pipe size

miatafrank

I have a customer with an undersized hydronic expansion tank. The new properly sized tank that I've bought has a 1 inch connection and is a floor standing unit to serve his 250,000 output boiler. The existing boiler main is 1 inch copper coming off the top vertical then turns horizontal using a tee instead of an ell. Instead of installing the tank on this horizontal run as it heads out towards the radiation, someone ran 1 inch copper out the other side of this tee and soldered on a 1 in.C x 3/4F adapter and  then threaded in the tank. Looks like this was done due to space considerations. My question: Can I run 3/4 in. to the new tank and from the same side of that tee as it is now? My plan is to pull a vacuum on the system, unscrew the old tank and then quickly install a full flow 3/4 in. ball valve at that adapter. Then I can relax and pipe in the new tank. Thanks, Miata Frank

JohnNY

¾" is fine.

However: "My plan is to pull a vacuum on the system, unscrew the old tank"



You'll still need to deal with a lot of water from the pressurized tank.

miatafrank

Hydronic exoansion tank pipe size

Thanks for your response. This is my first time on The Wall and I look forward to visiting often from now on. Yes, I will make sure to get the pressure/water out of that old tank.

I can easily add a drain valve. Thank you.

Yes, it is only 1 inch copper off the boiler then across a couple of feet and then there are three tees spaced close together to supply the three zones. One zone goes to baseboard radiation serving mainly the kitchen, another zone goes to a1st floor family room with in- floor radiant tubing, and the last zone supplies the bulk of the house (1st and 2nd floors) and these are the original iron main            (2 1/2 inch) and return (2 inch ). The sizing charts from various manufacturers all showed this sized tank. It is the 1 inch connection to the tank that got my attention. Also, the system is filled with water and I can pull a vacuum just by opening the boiler drain until the water stops. Tell me if this won't relieve the water pressure from the tank. When I remove it, I expect to get only some residual water coming out.  I could cut the 1 inch and push a shark bite valve on, but if 3/4 inch is good then I'll pipe with that.

M Lane

Add a drain

if not already there, downstream from a service valve. Either a boiler drain or a cap & chain ball valve. I have installed 3/4" piping to X tanks on 10-story apartments and schools (Millions of btuh's)

Mark Eatherton

Right on...

We are trying to get the installation of a drain valve between the isolation valve and the tank as a minimum code standard in the USEHC and UMC.



Should have been a requirement a LONG time ago…



ME

M Lane

Good opportunity

for a freeze kit. Kind of expensive, but they really pay off at times. I have a General. Of course, don't bother if glycol is involved

Mark Eatherton

Shark Bite stab and go...

I think they even make a stop and waste ball valve that would allow you a mean of being able to relieve the pressure from the diaphragm for purposes of testing.



Cut the copper pipe, stab the ball valve onto the pipe, close it first, and you are on the home run stretch.



Technically speaking, 1/2" is plenty. Its not like the water in that section of pipe is going to be moving at an excess velocity situation…



ME

Steve Whitbeck

pictures

I would like to see some pictures of the near boiler piping.

3/4 inch pipe is big enough for the tank but 1 inch IS NOT big enough for a 250,000 BTU boiler.

Sounds to me that you now have more tank than was needed.

miatafrank

Hydronic exoansion tank pipe size

Yeah, in the spring I'd like to go back and re-pipe the near boiler piping. The home owner got a couple of guys to do the new boiler 'on the side' a few years ago. They should have done a better job.

EBEBRATT-Ed

1 1/2"

250,000 sounds like the boiler should be piped with 1 1/2"

hot_rod

plenty of tanks

piped with 1/2 copper or pex for remote mounting. The main thing is to make sure it ties into the piping near the inlet side of the circ pump.