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Expansion tank replacement for a Zilmet

A ten year old MZ boiler's expansion tank's bladder has just started leaking. The pressure loss is subtle (very slow) and there is a faint odor of the treatment chemicals when air is added to the tank.
The tank is a little odd as the Schrader valve is in the shell instead of the head. Standard 2 gallon tanks are about the same size but with the valve on the head they will not fit in the boiler.
Zilmet's sites don't seem to have the same tank listed. An email to Zilmetusa was rejected because of an "unknown user".
I found a supply house which claims to have a replacement tank but the cost is 5 times!!! the cost of a 2 gallon tank.
The attached photo shows the nameplate. Unfortunately, the curvature of the tank makes some of the text blurred.


  • Steamhead
    Steamhead Member Posts: 14,834
    How big is the tank- height? width? A standard replacement might work...........
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • SWEI
    SWEI Member Posts: 7,356
    I suspect this is one of the Zilmet Flat family, in which case there is no drop-in replacement of which I am aware.
    I would give them a call 401-884-4943
  • kcopp
    kcopp Member Posts: 3,818
    Can you get a pix a bit farther back....? It looks similar to the expansion tank in an Embassy Axia.
    I have dealt w/ a bunch of zilmet tanks lately. They seem to have a short life. I have been leaving them in place and installing a Standard tank in the system close to the suction side of the circulator.
  • Eric_32
    Eric_32 Member Posts: 267
    I'm pretty sure I had one of those become waterlogged on me a couple years ago. The one I worked on was inside the boiler itself. Special order, more expensive, cold outside now... I also left it alone in the boiler, I popped in a Watts ext 30 outside the boiler, replaced the leaking relief valve, bled the system and was back in business.
  • Cold in Baltimore
    Cold in Baltimore Member Posts: 14
    edited February 2016
    Kcopp & Eric: Nice way to save $!
    Why not take the tank out and plug the hose fitting?
    Steamhead: The size is almost exactly like a 2 gallon tank. The 2 gallon tank fits nicely, except for the Schrader valve which hits the back of the boiler cabinet. (Yes, I could drill a hole.)
  • SWEI
    SWEI Member Posts: 7,356
    How big is the system? How many BTU's and roughly how many gallons of water in it? You may be able to get by with a smaller tank.
  • kcopp
    kcopp Member Posts: 3,818
    The only reason that I would not remove it from the unit was that the fittings on many of those wall hung European boilers are metric... try to find the right plug on the fly.
  • hot_rod
    hot_rod Member Posts: 15,015
    It will be a BSP thread, typically a 3/4 or 1"NPT plug will fit close enough , but it needs a gasket to seal.

    As I recall they had a short stainless braided connector to the tank with swivel nut and gasket.

    There is a Zilmet NA in Providence RI, try Scott Jacobsen there. Rare chance they may have that tank.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream