boiler is Weil McLain Gold CGa.

current circ pump is Taco 007-F5, installed on return side, pumping water down, and into the boiler.

I'm pretty sure this pump is under-sized, as the specs list a max head of 10 feet, and this system is used for heating the second floor unit of a 2-unit apartment. vertical distance from boiler to 2nd floor is wall over 10 feet, more like 16 feet. the apt has baseboard elements, but the temp in the unit never gets above 62-65. boiler temp is set at 220.

I'm looking to replace the 007-F5 with a Taco 009-F5, with a listed max head of 35ft. BUT, the 009 has a max flow of 10 GPM, compared to the 007's 23 GPM. Does this "upgrade" make sense??

Thanks in advance.


  • Hello, and welcome to Stack Exchange. I'm pretty sure the "maximum head" isn't the height of the highest loop, but rather the pressure (in feet of water) the pump can supply. Commented Jan 15, 2017 at 0:28
  • Many pumps are rated in feet for maximum head at the rated flow rate. Not many folks know that water weighs just under .5 lbs per foot. Measuring the rise is easy.
    – Ed Beal
    Commented Jan 15, 2017 at 2:13

3 Answers 3


The Maximum head of the pump is not to push the water up to the radiators, it is to overcome the friction loss of the flow of the water in the system. The installed pump should be large enough for your heating system. The water in the system is held up to the highest radiator by the water pressure in the system (look at the pressure gauge mounted somewhere on the boiler) A rule of thumb is 12 psig for a 1 story house, 15 psig. for a 2 story house and 20 psig for a 3 story house. Turn the boiler system off, go to the highest rad and open the vent. If you get water out then the pressure on the boiler is okay.If you can't get the temperature high enough check for water in the rads or baseboard units, vent all the air that may be in the heating elements. If all this fails call a boiler co. to fix the problem. One more thing, if you screw up and install too large of a pump you will get noise in the piping or radiation.

  • thanks for this info. i hadn't considered the difference in max head for closed systems vs open systems. based on the friction head calculation formula i found (linear feet * 1.5 * .04), it seems the system would need about 12 feet of head, which is still above the rated capacity of the circ pump. air has been bled from the system, but only the first few baseboard units get relatively hot, all the others are lukewarm at best. so i'm still leaning towards a water flow issue (no leaks found).
    – jklDev
    Commented Jan 16, 2017 at 0:49
  • did this heating system ever work properly or is it new?
    – d.george
    Commented Jan 16, 2017 at 14:24
  • It not new. Was installed about 10 years ago, and it never really worked all that well. Former tenants never really complained about it. Was hoping cranking the temp up to 220 would help, but still doesn't seem to be enough.
    – jklDev
    Commented Jan 16, 2017 at 14:33
  • I would add the pump. Good luck
    – d.george
    Commented Jan 16, 2017 at 15:32
  • so... on a whim yesterday, i added more water into the system, raising the pressure to about 22 psi. check a few hours later, water temp into first baseboard is now 118 (was 65 before). temp coming out of last one is 96 (was 44 before). pressure is around 30psi, when heat is being called. the housing on the circ pump is still REALLY hot. Too hot to touch for more than a few seconds. but this is how it's been since i started troubleshooting 3 days ago. not sure if that's normal. new pump has already been ordered, now i'm not sure if i still should install.
    – jklDev
    Commented Jan 17, 2017 at 20:56

Try these ideas: The pressure in the system should not rise to 30 psig.when heat is being called; check expansion tank. If it is a bladder tank , You need to raise the start pressure within 1 or 2 psig.of the new pressure.If it is not a bladder type then the tank is near flooded (too full) or too small. For the correct pressure setting I would measure the distance from the radiation down to the pressure gauge, divide by 2, and add about 2-3 psig to that number and that becomes the cold start pressure. Also check the pressure gauge and see if it is calibrated in pounds or in feet. Some gauges are in feet, which means that the 22 is actually closer to 10 psig. The gauge may be out of calibration and need replaced. On the pump, Too hot too touch is probably about 130 F.. Not too hot for a close coupled pump and motor. If you really are interested in the working temp look on the motor for the temperature rise, and add that to the ambient temperature. If its centigrade convert to degrees F. I should have asked earlier but is the copper tubing in the pump and radiation, 3/4" or larger as it should be and how many feet of baseboard radiation is installed? I still find it hard to believe that the pump is too small. Does the boiler heat only this apartment, is a series loop installation, (1 inlet and 1 outlet). Let me know what you find out.

  • the pressure gauge has both pounds and feet and I have been reading the right numbers. i checked again this morning with the heat running, it is around 26 psi. sounds like the pump is right where it should be, yay. the there's about 54 feet of tube/fin elements. entire loop is 3/4" copper line, with one exception. the system used to be cast iron radiators, which were replaced, so after the last baeboard, it taps into the old 2" iron pipe, to get back down to the basement. click the link for a visual of the layout. blue is the return. IMAGE_LINK
    – jklDev
    Commented Jan 18, 2017 at 14:29
  • lastly; if the water into the baseboards is close to the temperature of the hot water pipe leaving the boiler then every thing is pretty good. One thing you could try is turn the thermostat up in the apartment and see if the water temp rises and does the apartment get hot. Hope everything works okay Glad to be able to help
    – d.george
    Commented Jan 18, 2017 at 15:02
  • I had 1 more thought, You said that the return was down an old 2" pipe.If the 2" pipe is not completely filled with water, this could affect the flow of water in the system. (On a normal hot water system the down pipe cancels the up pipe head thus allowing the pump head to push the water through the system without having to use the head of the pump to lift the water to the radiation). This could be why the original pump seemed too small for this system. Since you are replacing the pump anyway this problem will be eliminated.The new pump has enough head to make the system work.
    – d.george
    Commented Jan 25, 2017 at 0:06
  • If you read this ,how did the new pimp work. Bell and gossett makes a 3 speed NRF 25 with a max head of 18feet and 25 gpm. Let me know.
    – d.george
    Commented Jan 31, 2017 at 20:19

If the existing pump turns out to be too small to provide adequate heating, I would return the 009 pump,which has a lot of head, and instead purchase a 0015 IFC 1/20 hp. 3- speed taco pump. The 3 speeds selected at the pump. You get 3 choices to provide the best possible results. Flows are approximately 11 -15 -16+ feet of head and 11 - 16 - 18 gpm.This pump would work great on your system. I checked pricing of pumps at "supplyhouse.com" and found that the 009 pump costs about $230.00 while the 0015 costs about $85.00. The 009 pump costs so much more because of the high head of the pump.

  • i was able to get the 009 from amazon for around 160. i did consider the 0015, but it's been discontinued, so i was worried about that.
    – jklDev
    Commented Jan 20, 2017 at 12:46

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