I noticed my hydronic floor heat was no longer heating, and the circulator pump was extremely loud. This system was new in 2009 with one valve, pressure tank, and electric boiler replaced in 2021.

It sounded like it was likely a bad circulator pump so I ordered a new matching pump - Taco 0011-BF4 - I ordered a Taco 0011-Bf4-J to replace it.

The pump came today so I removed the old one - first shutting the valve above and below the pump. The pressure tank says it is charged to 15 psi so I wasn't surprised when I heard a small hiss when undoing the bolts for the old pump. But after that I expected a drip, and got nothing at all - taking the pump off it is completely dry.

Here's a photo of the whole system (hot water heater (hydronic only) to the right):

Hydronic system

Shouldn't there be water in this section? (I last tried turning it on about 48 hours ago) If so, what could cause it to be dry? I don't see any valves closed other than the two I closed to remove the pump - but admittedly don't understand it all. I've ready of air trapped in the system but was under the understanding that the supervent at the top should prevent that. Am I missing something?

  • Not an expert, but you probably have a blockage somewhere in the system. I think that pump is on the return side, so the blockage will be before it. A good plumber might be the best bet for finding the blockage fast, but if you have the time can probably do it yourself.
    – crip659
    Commented Jun 29, 2023 at 11:45
  • There is a plumbing device in the horizontal run of pipe at the bottom of the plywood sheet. It has a red tag on it and there is an air gap fitting below it. Could you either take a clear photo of the tag and add it to your post, or say what the tag says? My gut tells me that this device is preventing water from reaching your pressure regulator (the green Taco device above the pressure tank). But I can't identify the device with the red tag. What is it?
    – MTA
    Commented Jun 29, 2023 at 12:33
  • I would look for a bleed valve and purge the air out of the system. That pump will fail without water going through it. That is a cartridge pump so you need to get a replacement cartridge, much more cost effective then a new pump. Oh well you now have a spare pump, purchase two cartridges and you should be set for life.
    – Gil
    Commented Jun 29, 2023 at 17:41

1 Answer 1


just because the expansion tank has a sticker saying precharged to 15psi [which they all do and come that way from the factory] doesn't mean it actually has 15 psi of air in it. you have to check it with an air pressure gauge to know.

from the clarity of your picture :

  • I see what looks like 4 zones total - 8 vertical copper pipes attaching to pex, 1 supply and a matching return = 4 zones. But I only see 3 gold zone valves?
  • I don't see any way to air bleed the zones. There's no valve located in the correct place to do so. So if you have all your ball valves open and the green automatic fill (set to ~ 12 to 15 psi) located vertically between the expansion tank and the supervent at the top which looks to be a Spirotherm spirovent air eliminator - you should be able to find a tag on it to find out the exact make/model.

The air separator, regardless of which kind today, does not magically remove any and all air. You have to fill and manually bleed the entire system to 99% air free. Then as the system runs, the circulator moving the water, the air separator will remove the last bit of entrained air in the water (microbubbles) to where the water is air (oxygen) free and will not rust/corrode the system and give best heat transfer.

With what looks like no way from that pic to bleed any of those 4 zones you will initially fill it until ~15 psi of air is compressed at the highest points in the system... which might be 3/4 full of the hot water tank and air everywhere else... you likely have all air in all the pex pipes that run up and above. Yoy need to manually open one zone valve at a time and then open the fast fill lever on the automatic water feed to water flows into the system at full force & speed to push air up and around the zone (pex). Then close zone valve and do each zone.

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