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Boiler Taco 007 and Pressure Problems

ipman Member Posts: 15
Hello all,
Background - I have baseboard water heat in my house powered by a 2007 Weil-McLain 140K btu natural gas boiler with 4 Taco zone valves and 1 Taco 007-F5 pump. This year I've been hearing Taco 007 pump noise in my pipes upstairs. At one point water pressure was under 10 PSI and I added more water to get it up to 20 PSI (if I don't add enough water, it sometimes drops below 10 PSI and the pump doesn't work). This is 2 story house with basement. Last night baseboards were not very hot upstairs. Taco 007 pump did not seem to be pumping. Today I checked the pressure gauge and it was at 30 PSI. After draining water, water pressure dropped to 20 PSI taco 007 was working again. There is no auto-feed for water supply, only a shut off ball valve for manually bringing new water into the system. I have had pressure variations with this boiler before but not as extreme. I have noticed that pressure is higher when the zone valves are off and when there is a call for heat/valves open, the pressure drops. The expansion tank sounds hollow when knocking it. The two auto air vents at the boiler leak when the cap is loosened but I hear air released and need to scrap cap back on to stop water leak. The plumbing for my boiler is a little spaghetti like. The expansion tank is installed after the taco 007 supply side. It is installed after a T to other zones but before the zone valves so it doesn't seem like it is installed in an ideal location.
Long term - I get the feeling the piping needs to be redone with the expansion tank installed before the taco 007 and a better air eliminator setup. Zone valves and plumbing need to be redone to be a lot cleaner and need more shut off valves to isolate things but that is not something I want to mess with right before a cold winter. Any other advice would be appreciated.
Short term - I am planning to drain the system, replace the two auto air vents at the boiler (see pictures) replace the 15 year old Taco 007 with a Taco 007e ECM pump (mind as well upgrade, especially with 4 zones right?), replace the 15 year old expansion tank with an Amtrol No 30 expansion tank (checked the manual and looks like right size for 140K BTU) and refill the system and bleed it. It will cost me roughly $285 for the parts so I don't want to spend a lot of time testing/draining/refilling to save the 15 year old parts. Does this sound like a good idea short of redoing all the piping?
Thank you for your help!


  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    The expansion tank is on the outlet side of the pump? That is the wrong place -- it needs to be on the inlet side, and it should be precharged to the system cold pressure (usually 12 psi, but sometimes on taller houses 15). Unfortunately, the only way to check that is to isolate the tank from the system, drain it of all water, and check the air pressure, and adjust it as necessary. The tap test is next to useless on modern bladder tanks. You would need to do that with a new tank as well -- they don't always come precharged to what you want.

    If the tank is functioning properly the pressure at the tank shouldn't vary by more than a few pounds between hot and cold.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gilmorrie
    Gilmorrie Member Posts: 185
    Don't just throw new parts at it. You should call an experienced pro.
  • hot_rod
    hot_rod Member Posts: 22,144
    Its hard to see where the exp tank connects. IF it is on the return it is okay, you are pumping away via the wide open cast boiler.

    If not, a "hack" would be to connect the tank to this purge valve :) Get a 5' wash machine hose. Screw a 1/2 fip X hose adapter on the new tank connect the hose from boiler drain to tank. Then it is at the boiler and you are pumping way.
    At least to try and see if it fixes the air issues.

    Usually you can wiggle an expansion tank enough to determine if it is waterlogged or an empty steel can.

    TIP! treat every expansion tank you unscrew as a full waterlogged 30 lb piece of metal. Be prepared for that weight.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ipman
    ipman Member Posts: 15
    @hot_rod Thanks for the diagram. Instead of the temporary fix, I can add a couple of t's on the return pipe in your screen shot under the shut off valve, one going to water supply and another going to a new expansion tank. This will allow me to cut out and cap off the current expansion tank/water supply piping connecting to the supply side piping of the boiler.

    This would better match how your diagram looks, would you agree?

    Would you stick with manual ball valve for water supply or go with an auto feeder?