Air entering on low pressure side

Dan_22

Since the negative pressure is always going to be on the suction side of the pump maybe replacing just the section of piping from the inlet of the pump to the tank with copper would solve your leak problem. I would also complain to the pex manufacturer about this problem. If installed correctly pex systems should hold a vacuum.

jim_59

I've got a wood fired boiler w/500 gallon storage tank. I have a circulator which draws from the tank through the boiler heat exchanger through the pump through a exchanger to the domestic water heater and back to the storage tank. My problem is the pump draws air through the pex fittings and eventually loses it's prime. I don't want to relocate the pump, nor do I seem to get the pex fittings to stop leaking. So I wanted to put in a air vent at the suction of the pump, but I think they only vent if pressurized. In this case since it is an open system it is not pressurized so I don't think the a standard vent would work. Are there any vents that will work in a vacuum or any other options?

Thanks,

[Deleted User]

Leaks...

don't fix themselves. Fix the leak first. second, if at all possible, move the pump so that it pumps away from the boiler, which I assume is an open vessel. That is the PONPC. If you pump away from the PONPC, all pressure differential that the pump generates will be presented in the form of positive pressure.

At present, assuming that the pump is pumping toward the PONPC, all of its press diff is being seen in the form of negative pressure, and it is possible that you could be sucking in air. Adding an AV will NOT cure your problem, in fact may make it worse.

ME

jim_59

Pex leaks

I'll work on the fittings first. I wasn't sure if the pex fittings were supposed to hold a vacuum. What about the Hoffman model 76 vent. It appears it will work on vacuum, does anyone know where I'd get a cross section of the 76 to see how it works?