What kind of expansion tank and connection is this?

Bob Vennerbeck

I'm trying to help a friend troubleshoot an older hydronic system in a two story house in Brooklyn. It's acting like the expansion tank is waterlogged - but I've not seen this particular arrangement of horizontal tank screwed into what looks like a proprietary fitting, and don't want to suggest that 'simply replace with a modern bladder tank' is going to be that simple.

Tank is date-stamped 7-62, and system is working, but started 'burping' the safety valve occasionally. He's found that keeping the system fill pressure around 10# is a 'sweet spot' but we all know that ain't the right way to make this work.



And yes, we've already talked about correcting the flue on the separate water heater.



Thanks for any thoughts!



Vbob

billtwocase

savings!!!

Someone saved a few $$$ by not using some black iron nipples and fittings. It is an early bladder type expansion tank with no means of checking the air in it. That is installed where the old expansion tank was plumbed in. It would have been strapped between the floor joists, and plumbed in copper with a stop/ w waste valve. This is the system's flow check that it is attached to. I would say that the tank is OK, otherwise the relief valve would go off constantly. I would still have it corrected, for if it does get waterlogged, it may break off and then the problems begin

Bob Vennerbeck

I thought that might be a flow check...

I thought that might be a flow check... hadn't seen that particular pattern before. The notion that the existing 1962 tank is already a replacement makes sense - and puts us back to plan 'A' of replacing the 1962 tank with a 1/2" nipple, ball valve, nipple, elbow, and new tank; all suspended from a pipe hanger into whatever meat can be found overhead.



The brass adjustment screw on the top of the flow check is 'dribbling' - earlier thinking was that it was some kind of air bleed that wasn't quite seating. Now I would suspect that there's a gland nut up top that might benefit from some wire brushing and repeat applications of penetrating oil before any attempt to tighten it...



Plan 'C' was to crack the union, replace the unknown fitting with a tee, and pipe off to a new tank, but that would eliminate the flow check, and there's not another convenient place to put one at this point in the season.



Plan 'B' is Belize for the holidays, where the owner of this doesn't need the heat, but can worry 'bout the folks back home....



Thanks for pointers!



Vbob

Mark Eatherton

I aam told...

that the ORIGINAL diaphragm tank, s invented by the good folks at Amtrol, was "charged" with gas by placing a pre-determined size chunk of Dry Ice in the can prior to welding it shut. The CO2 would then exert approximately 12 PSI on the air side of the tank.



The rubber bladder that separates the fluid from teh gas is a permeable material, and the gas charge will diffuse through the walls of the diaphragm, eventually requiring recharge. Hence, the addition of the Schrader valve to check and change the charge.



Don't forget to incorporate a drain cock between the isolation ball valve for the tank, and the tank itself. This will allow you to take the water side to zero in order to properly diagnose the air charge on the tank.



Belize eh.... Ahhh... Snorkel divers retreat ;-)



ME

Henry

Flow check

That red thing is an Armstrong Flow Check valve, The lever will manually open or close it. Somebody had a little too much imagination in connecting the expansion tank there!



Enjoy the water in Belize! I hope that you are also fishing there!