Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

No heat 2nd floor - Mid 1950's Monoflow T System

PerryHolzmanPerryHolzman Member Posts: 145
edited September 10 in THE MAIN WALL
Hi everyone. Sorry I've been away. Its been an interesting summer and I've been busy.

Since I'm a semi-regular here I suspect I know the problem. But, figured it would be best to verify that and likely learn something I don't know.

The weather has cooled off and my heating system has automatically started as it should. But, the 4 cast iron baseboard radiators on the 2nd floor of the house are cold; and the 5 cast iron baseboard radiators on the 1st floor are warm. Mid 1950's Monoflow T system (1 1/4" iron pipe, 1/2" risers/returns)

Fall 2006 replaced original boiler and B&G pump with a a Vitodens 200 with an internal primary circulating pump, a low loss header, and a secondary Taco 007-F5 circulating pump. Both pumps are currently running (or at least the motors are). Water is being circulated through the low loss header by the primary pump.

Perry's theory: Secondary pump is not working properly (shaft broke, impeller degraded, etc)- and primary pump cannot develop enough head to circulate to 2nd floor of house, especially with the low loss header.

I've discounted air binding as why would all the 2nd floor radiators and none of the 1st floor radiators air bind. I could see that if only 1 radiator was cold.

What other things could it be?

Additional questions? If I'm going to drain the system to replace the Taco 007-F5, should I also replace the primary pump as well (or are they known to last for multiple decades). Should I change the air charge/pressure maintenance tank and the make up water reducing pressure valve as well? Any other suggestions on overall system maintenance or improvements after 14 years?

Note that I rebuilt the Vitodens 200 last year with a main control board (it failed), a new fan (bad vibration), and a few other parts. It runs well.

Life is worth living if you do it well...



  • STEVEusaPASTEVEusaPA Member Posts: 4,362
    System pressure? Confirmed with good known gauge?
    I’d try purging first.
    Air rises and would naturally gravitate to the 2nd floor.
  • PerryHolzmanPerryHolzman Member Posts: 145
    @ STEVEusaPA

    Actually, with the way the riser to the radiators are piped off of the loop pipe - I'd expect any air that got into the system at the boiler or Low Loss Header area to 1st get into the 1st floor kitchen baseboard radiator, then the 2nd floor bathroom, then the 1st floor living room, etc...

    The expansion tank air pressure was 10 psi. I raised it to 15 (Tire guage). The boiler pressure guage reads 5 lb higher than that, and moved appropriately when I raised the expansion tank pressure.

    It will likely be tomorrow AM before I can see if this works. Currently the boiler is shut down.
  • ratioratio Member Posts: 2,545
    Is the expansion tank a bladder-style? You must isolate & relieve any water pressure on it before setting the precharge.

    ratio's theorys: either 2nd floor is air bound, or low static fill pressure.

  • SuperTechSuperTech Member Posts: 1,390
    I wouldn't be sure its not air until I tried to bleed the cast iron baseboards. Check that and then check amp draw on the secondary pump, if possible.
    Expansion tank pressure does have to be set with the tank removed. Considering adding isolation valves for the expansion tank and circulators.

  • Robert_25Robert_25 Member Posts: 206
    I used to live in a house with the same type of system.  Any air in the system always ended up in the 2nd floor baseboards.
  • PerryHolzmanPerryHolzman Member Posts: 145
    edited September 11
    Thanks all. I had time to bleed the system tonight... or rather part of the system. There was (and still is) a lot of air in the system. Air bladder pressure dropped significantly again, with a corresponding pressure drop on the boiler gauge.

    My theory at this point is that the air bladder has a small leak - and leaked air into the system; air binding the radiators.

    At the same time - as I was able to bleed air until there was no more obvious pressure on the 2nd floor... that the automatic makeup valve/pressure regulator is not working either (or I would have had water pressure maintaining the appropriate pressure - and could have bleed all the radiators) .

    The nice think I observed was that where I could bleed to water... the water was only light grey and not totally black (as was the original water we drained out of the system in 2006).

    Good thing its early September. Easily time to get the contractor in to replace these two items before cold weather actually gets here (and I will let the contractor do this).

    Is 14 years a typical life for them?

  • mattmia2mattmia2 Member Posts: 1,729
    Since there isn't a lot of flow in the emitters in a monoflow system, there usually isn't enough velocity to pull the remaining air out, the only way it will be able to remove air is by it dissolving in the water so a monoflow system will be more prone to collecting air in the emitters and flow is more sensitive to being disrupted by air in the emitters.

    If the air elimination at the boiler isn't already a microbubble scrubber type, adding one while you are repairing the prv and expansion tank would be a great idea.
  • STEVEusaPASTEVEusaPA Member Posts: 4,362
    By your description you’re not bleeding/purging correctly. You have to keep the pressure up around 20+ lbs. until all air is purged.
  • PerryHolzmanPerryHolzman Member Posts: 145

    But where is the air coming from?.. This is a sealed system with no signs of leaks (and all the piping except for the outer wall risers and returns to the 2nd floor are visible). Never had air in the system for the previous 14 years.

    The only source of air is that air bladder... and pumped it up again yesterday - so it appears that it added 2 charges of air to the system by leaking.

    Also, I bled air until there was no more pressure on the 2nd floor - and no water ever showed up. That means that the auto-fill pressure regulator is not working and not supplying makeup water.

    I'll have the contractor replace the air bladder and the make-up supply pressure regulator. It does not surprise me that they could fail... I've spent most of my life working in industrial and power plants - and nothing works forever. I've also read about failed bladders before on this forum.

    I'd even guess that the make-up regulator may never had been asked to supply any make-up water for the previous 14 years. It would not surprise me if its frozen.

    Have a great day,

  • STEVEusaPASTEVEusaPA Member Posts: 4,362
    edited September 11
    You add water to the system, this is static pressure. Without static pressure, you can not lift the water to the top of the system, nor can you eliminate the air.
    You have to keep the pressure up at about 20psi (circulator off), while you bleed, until you purge all the air out of the system.
    If you need, say 15psi, just to push the water to the top of the system and the air out, every time you drop below that while you're bleeding, you will get the effect of no water coming out of a radiator, and no air.
    Pumping up the bladder tank isn't doing anything for you if the tank isn't holding it's charge. It needs to be isolated from the system (or system dropped to 0 psi) and pumped up to the pressure your system requires while operating.
    Most systems, especially older ones, will simply lose some water.
    So measure from the gauge on the boiler, to the top of the highest radiation in the house X .433 will equal how many psi. you need just to get you to the top. Then add 5 psi. That's what you need to keep the pressure at while purging, and that's where you need to keep the system to prevent air problems.
    It's also the pressure you need at your expansion tank and your fill valve.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,223
    What @STEVEusaPA said in his last post is the correct procedure
  • PerryHolzmanPerryHolzman Member Posts: 145
    Its a great weekend Steve @ Ed.

    I am well aware of static pressure and know how to calculate it.

    For clarification: The distance from the makeup water reducer/regulator to the top of the radiators on the 2nd floor is 10 ft (4.33 lb static PSI)

    It's 11 ft to the center of the expansion tank.

    Its 14 ft to the boiler gauge (6 PSI static head)

    So, the makeup water reducer regulator is not adding water when the static head is 4.33 psi at the regulator and there is no indication of pressure in the bladder for the expansion tank.

    Add that to the sheer quantity of air in the system... which could only have come from a leaking bladder (you cannot get that much air from the entrapped air of the qty of water in the entire system).

    I've called the heating contractor to do the repairs (although I am not on their "urgent list" as they have people without any heat). They did not question my diagnoses.

    I've also asked them to add a valve between the expansion tank and the system so it can be changed (or tested) without draining the system.

    In addition I asked to add an additional pressure gauge, again with a shut off valve so it can be changed/tested without draining the system. That gives me (and anyone else) a much better understanding of where things are at with the system as I don't trust the boiler gauge to be very accurate.

    Have a grand weekend,

  • STEVEusaPASTEVEusaPA Member Posts: 4,362
    edited September 12
    Oh boy...You're NOT getting air from a leaking bladder tank. You would instead have a water logged bladder tank.
    A simple stand alone gauge that screws into a drain (garden hose fitting) is all you need to confirm system pressure.
    Yes the Webstone Expansion Tank Valve is a good idea.
    No offense, but if you new all about static pressure you would've correctly solved this problem fairly quickly :).

    So for any other homeowners who stumble across this conclusion;
    Problem: not enough water in the system-caused by possible leak, and fill valve not supplying the boiler with make up water.
    Solution: new fill valve, new expansion tank (if confirmed it's needed), proper fill and purge as outlined above. Might as well replace the relief valve while the system is drained.
  • mattmia2mattmia2 Member Posts: 1,729
    I'm not convinced that the leak @STEVEusaPA refers to can't be in the diaphragm of the tank. It requires both a failed prv and diaphragm for that to happen. The diaphragm slowly leaks the air out, some collects in the radiators, some is removed by the air elimination. The diaphragm expands in the tank and takes up some of the water that was in re radiators. Since the leak in the diaphragm is slow and the prv isn't filling the system, it still has some air pressure that keeps the water on the system side.

    If this theory is correct, if you use a garden hose or the manual lever on the prv to bring the system up to pressure, water should start leaking in to the air side of the tank. If the schrader is the low point and you release the tank pressure with pressure in the system, you should get water out of the schrader.

    Also possible(and more likely) the schrader on the tank leaks a little and the air leaked out that way making space for some system water inside the water side of the tank and since the prv is not working it didn't refill the system so air cam in through automatic vents to take its place.(although I don't think it ever went in to vacuum since it was at 10 psig so that seems less likely now that i write it out and i can't really see how it isn't the tank).

  • PerryHolzmanPerryHolzman Member Posts: 145
    Thanks "mattmia2" Its the only explanation for the quantity of air involved as there are no evidence of any system leaks - and the system has been tight for the previous 14 years since installing the Vitodens 200 without any air buildup (I do occasionally vent the radiators - never seen any air before, which is why I didn't think of that as a possibility initially).

    I've run a calculation on the volume of the system. The 1 1/4" pipe base loop and the 1 1/4" copper tube used to relocate the boiler (a Vitodens 200) to the wall come up to 5.22 gallons.

    The risers, baseboards, boiler, and hot water loop to the indirect has to be less than that. So less than 10 gallons to fill the system.

    If you take 10 gallons of raw air entrained city water you might have 1/8 of a cup of air in 10 gallons of water. There was vastly more air than that in the system. So where did the air come from if not the expansion tank?

    Also, who says the expansion tank is not mostly waterlogged. I'm not superman who can see inside a steel tank. Even if the diaphragm was completely ruptured I'd still be able to add air to the system via the Schroeder valve and re-pressurize the system.

    I'll let everyone know when I can test the existing expansion tank, after its removed. It a standard commercial heating system expansion tank. I've seen plenty of pictures of it on many of the threads and the cost is relatively low per a web search.

    Life is worth living if you make it so,

  • STEVEusaPASTEVEusaPA Member Posts: 4,362
    @mattmia2 I don’t know your background but what you describe, absolutely can not happen, and you’re wrong-plain and simple. It would defy the law of physics. You’re just not answering the question 'where did the water go'? The OP insists no leaks, despite the common knowledge that all systems lose a little water over time.
    Even if the system goes negative from not pumping away from the expansion tank and pulls in air, unless water leaves the system the pressure would rise.

    You and the OP are looking for some fantasy scenario to explain something plain and obvious-not enough water being maintained in system to properly purge system.
  • PerryHolzmanPerryHolzman Member Posts: 145

    My guess is that the missing water is in the expansion tank, which would not violate any laws of physics.

    The quantity of air that appears to exist is "in part" the quantity of air that expands as the pressure is reduced to atmospheric.

    Have a great day,

  • mattmia2mattmia2 Member Posts: 1,729
    The water went in to the expansion tank. Since the volume of that system is relatively small, the expansion tank under normal conditions even at setpoint is nearly empty. Without doing the math(and some of that math would involve compressing the precharge at cold fill which would involve the accuracy of the prv and the gauge you used to precharge the tank) I would guess that the tank holds at most a cup or 2 of water. If the leak in the diaphragm is small like a pinhole and the precharge is a little higher than the cold fill pressure, that air will leak through that hole until the pressures equalize. that will allow the diaphragm to expand on the water side and let more water in the tank to match the air that is now in the system.
  • STEVEusaPASTEVEusaPA Member Posts: 4,362
    Wrong and wrong.  Re-read the ops post and comments. No water or air coming out of the radiators on the second floor, fill valve not adding water to keep pressure up when trying to bleed/purge. 
     I just had a deja vu moment. Am I in a boiler room talking to 2 engineers?
  • stonebutsonstonebutson Member Posts: 21
    What circulator did you take off? Is the 007 a good match (I doubt it)? I don't know how big the system is but monoflows usually require a higher head circulator to get the gpm right - no heat to the second floor is a classic symptom
  • PerryHolzmanPerryHolzman Member Posts: 145

    What circulator did you take off? Is the 007 a good match (I doubt it)? I don't know how big the system is but monoflows usually require a higher head circulator to get the gpm right - no heat to the second floor is a classic symptom

    The Taco 007 has been installed since October 2006 when the boiler was changed from the original mid 1950's to a Vitodens 200 with a Low Loss Header. There has never been a heating problem on the 2nd floor until now. So while it might not be the "perfect" pump; its adequate for the job.

    The heating contractor in 2006 said they were going with that pump because they carry it on their trucks as its the most common pump they use. The flanges have ball valves installed so that the pump can be changed without draining the system. I believe that is a normal option from Taco.

    Have a great day,

  • ZmanZman Member Posts: 5,948
    edited September 15
    An air lock is far more probable than a broken shaft. Shafts do occasionally break, just not very often. If the shaft is broken, you cannot simply change the cartridge and avoid the wet side.

    Feeling the pipes with you hands is a simple often overlooked troubleshooting tool. If the supply and return are different temps, you have flow.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • PerryHolzmanPerryHolzman Member Posts: 145
    edited September 22
    The verdict: Expansion tank bladder leak combined with non-functioning auto fill valve and questionable if air vent working right.

    Thanks to those who pointed out the failed expansion tank bladder as the issue.

    Expansion tank was at least mostly full of water (I did not measure how much water came out - but it was a lot). Very small leak (a faint hiss when you hold the water nozzle to the ear with 8PSI pressure inflated bladder).

    So the failed bladder is the source of the air in the system, and where the water from the upper radiators went (the entire system holds less than 10 gallons of water). The frozen auto fill valve explains why I could not fully vent the upper radiators once I bled off the air pressure.

    Local heating contractor technician (and one of the people who installed the system in 2006) says that on average they find failed expansion tank bladders anytime after 10 years in service.

    Also replaced the vacuum breaker back-flow valve and the air vent. Added an isolation valve for the expansion tank. It can now be replaced without draining the system.

    Added a place for a pressure gauge with an isolation valve. The field crew had not heard that I wanted one... They will return in the next day or so when they have a gauge. Likely 5 minutes to install.

    Have a great day,

Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!