Air Bound Hot Water Heating System Repairs:

How to remove un-wanted, air from noisy or air-bound hot water heating system pipes, radiators, convectors, and baseboards using a portable pump and drain valves on the heating boiler.

Here we detail exactly how to hook up a transfer pump to force water through and air out of an airbound or air-logged hot water heating system. This pumping procedure is also used to add antifreeze to hot water heating boilers.

Q&A on Pump Procedure to Fix Air-Bound Hot Water Heat Systems

These questions & answers about how to use a pony pump to force air out of an air-bound hot water heating system and its pipes, radiators, baseboards, were posted originally at AIR BOUND HEAT SYSTEM REPAIR by PUMP - be sure you read that material too.

[Click to enlarge any image]

On 2018-01-08 by (mod) - if you are sure that the circulator is running

Carla

If you are sure that the circulator is running (or perhaps you only have one circulator feeding both zones) and when there are no manual air bleeders you could try to open, we're left with having to call the heating service tech to

- check that there is not a stuck check valve on the cold zone

- check that the zone valve is opening on the cold zone

- check that when the zone valve opens it is turning on the circulator

- check for and remove air in the old zone piping

On 2018-01-08 by Carla Wingle

Ok I have a hot water boiler e zones only the upstairs gets heat.

It's freezingbon the first floor.

The water pipes from the boiler are hot but the baseboards are not. There aren't any breeders on the baseboards either. So I tried everything poss it just will not work help

On 2016-12-21 by (mod) -

Very good going, Rod. Your description of forcing water through a heating system to purge air when there aren't all the shutoff valves one might like is likely to help other readers.

Air leaks can occur into systems even when there's no water leak out, though I find that counter-intuitive.

An example claimed by a MN plumber with whom I worked recently was that of air leakage in at a circulator pump mounting flange, on the suction side of the pump.

I was dubious as even if there's no water on the floor, I'd expect to see some signs of water leakage out at the same point when the pump wasn't running - if not a wet area at least mineral efflorescence build-up.

Air might also leak INTO a hot water heating system at high-located air purge valves if the valve is leaky and defective. When the heating system cools and pressure drops in the piping an air leak into the valve might occur.

On 2016-12-21 19:22:52.975683 by Rod W.

Figured it out. I had a couple of valves turned off that circulated through the hot water storage tank. That was the problem. And turns out, yes, I can use the drain to push water through the system. Now if I can just figure out the air leak, I'll be all set.

On 2016-12-21 by Rod W

This question is asked down in the comments but I don’t see an answer, so here goes:

My system does not have a service drain at the hot water riser pipe. In the past I’ve closed all the zones and the return at the boiler

I connect a hose to the drain faucet on one of the zones and using the lever on the city water pressure regulator, I up the pressure until the boiler relief valve opens, letting water out into the drain.

I then open the zone faucet and let the extra pressure push the water and air out

. It works okay but it’s cold standing outside for that long and I’m not sure I’m getting all the air. The cold water is probably carrying some extra air as well. I bought the pump but can’t get flow in either direction. I’ve attached the output to both the drain on the boiler and tried the reverse flow by connecting to the zone faucet. I’m quite sure I have everything open to create a loop

. Can I use the boiler drain in this way? If so, which way should I be trying for flow, through the drain or the zone valve side? Thanks.

On 2015-12-31 by (mod) -

Most regulators have a lever you can lift to bypass pressure reduction and feed at street pressure. That may be stuck; try a gentle tap.

Generally for a 2 story home the cold boiler pressure is about 12 psi. you're OK at 18 as long as when the boiler is fully heated-up the pressure doesn't exceed 30 psi - if it does the relief valve should spill.

On 2015-12-31 by chris p

It seems that when I was increasing the pressure by opening the regulator valve on the intake, that I may have damaged it and it is stuck open.

Currently I lowered the pressure to about 18 PSI then closed off the water intake. I am waiting for a heating guy to come take a look at the the system but for now I can at least heat my home.

On 2015-12-30 by (mod) -

It can be difficult to get all of the air out of piping in a hot water heating system, Chris, particularly if there are long piping runs, horizontal runs or air traps.

The procedure described above uses a separate pony pump to force water and air through and out of the system - a procedure intended for cases when just upping the feed pressure into the boiler isn't enough to force out the air.

You might also check to see if you have air bleeder valves you can open or that should be venting automagically at high points on the heating zones in your home.

On 2015-12-30 by chris p

I have a boiler and a 2 story house.

The heat upstairs was not circulating very well and it had lots of air bubbles that you could hear when the heat came on. I tried to bleed it but the pressure was very low and no water would come out of the return line, just air.

So I did some youtubing and I opened the pressure regulator valve going into the furnace for a few seconds and the water started flowing out the return line.

Once it seemed like all of the air was out, I closed everything back up and turned the furnace on. After a few minutes the pressure climbed up to 35-40 PSI and it started coming out of the pressure relief valve.

Since then I have tried a bunch of other things, I can lower the pressure back down but as soon as I turn the water back on it goes to about 20 psi, and then when a few minutes later it goes up to 35 or 40 again.

Anyone have any thoughts as to what could be happening?

On 2015-12-30 by (mod) -

Good question, Jerry, but yes it's possible either because of how piping is routed or because it's possible for there to be a partial air blockage; I see air blocks in long horizontal runs not just in high spots in piping.

On 2015-12-30 by Jerry S

We did major demo of our 2nd floor bedroom and bathroom.

Originally we had about 6 sections totaling about 35 feet including two short sections (~6') in bathroom but all were in a single loop controlled by one thermostat. The bedroom sections were replaced after the demo but not the bathroom sections. Now the bedroom sections work fine but the bathroom is cold

. I think the plumber accidentally left out the bathroom section from the loop but he says the bathroom is air-bound.

Is it likely that everyhting works in one loop except one section of baseboard?

On 2015-12-09 by (mod) -

Jim

Sorry to hear it's not working.

First do this: Disconnect your pump from the boiler completely and then try pumping into and out of the same big bucket of water.

If you see bubbles then the problem is pump cavitation or an air leak in the hoses.

Let me know what happens.

On 2015-12-09 by Jim

I have been doing this pony pump method for hours and air bubbles are still appearing in the bucket.

I've tried every air bleeding method I've found on the Internet and still can't get all the air out. Any suggestions on what to do? Or what else could be causing constant air?

On 2015-10-15 by RAS

My system does not have a service drain at the hot water riser pipe. It only has a drain at the bottom of the boiler.

Can I hook up the output side of the pump to the bottom drain valve and open the pressure relief valve into a bucket and have the input hose from the pony pump pull the water from the bucket?

I have a lower level room that has an air block and I think the pony pump method seems like the best approach. Everything else I've tried has not worked.

Comments:

(Nov 8, 2011) myron k lochridge said:
nice job od descibing how to purge hydronic heat system, i refer friends to this now as i describe it about the same way but easier for people to understand if they can read and refer back. thanks M K Lochridge

Question: one zone gets air bound a few days after I bleed air/water from the zone

(Dec 7, 2011) Bob Williams said:
i have one zone which gets airbound 10-14 dayszafter I bleed air/water from that zone, all other zones stay hot at all times

Reply:

Bob,

If you have a heating zone that keeps becoming air bound even after you've bled air out of the piping I suspect one of three causes:

1. there is a still larger air source or reservoir in the system such as at the boiler that needs to be removed

2. more likely, there is a leak in the system piping or in an air vent; if you are not seeing leaking heating water out anywhere, possibly the system is leaking air IN to the system when it's in an "off" or cool-down cycle.

3. not to be glib, but there could always be another cause we haven't thought of.

After checking out #1 and 2, let us know what happens - it will surely help other readers.

Keep in mind that air getting into a hot water heating system often likes to collect asymmetrically in just one or a few places; it does not necessarily travel uniformly through the heating system piping and radiating devices. So it's no surprise that we might find that just one heating zone gets air bound.

There could be a hidden leak out of that zone piping that lets air in when the system cools, but the air source could be elsewhere as I listed above.

Question:

(Dec 29, 2012) Gene Friedman said:
Awesome article! Just one thing - shouldnt step 2 preceed step 1 since you want the system on to check the heat and afterwards shut it off?

My system uses a B&G series 100 1/12HP circulator. When I compare specs with the pony pump shown here - the B&G is rated higher at around 2,000GPH. So would I need to get a much bigger pony pump to use this method? Thanks.

TW, Amazon shows this MPFVK115 pony pump rated at 1380gph not 365gph as stated in the article. (it could be the 365gph was @ max head pressure) but to compare apples to apples I am using the max gph figures which is at 0 head.

Maybe the fact that the circulator is installed on the return pipe and the pony pump goes into the supply side is the difference to be able to push the air out of the system - as opposed to suck it out of the system?

Reply:

Thanks Gene, I edited the original article accordingly, though not until Feb 2015.

The pump lift capacity you need is more a function of the building height of the highest zone through which you might need to push water, not the heating circulator's pump rate.

Question:

GITOBY said:
When purging with the pony pump and everything is connected as described doesn't the zone valve have to be manually opened in order for the water to circulate through the entire system?

Reply:

Thanks Gene Friedman and GITOBY for editing suggestions for the article above - I've merged your suggerstions into the article and Ive added some illustrations accordingly.

...

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• AIR BLEEDER VALVES
• AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE - alternative method

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