Bleeding Radiators Issue

timccarpenter

We have a 2 1/2 story house. I heard gurgling on the top floor and assumed the system must be low on water. I tried to bleed the top floor radiators (2). I get hissing air for awhile and then it stops before I get any water. Doing this when the system is not actively heating.

I attached my make up water hose to the system from the house water. Tried the same assuming it would backfill as I'm bleeding the radiator. Nothing.

Resting PSI in the system is 15..which should be adequate from what I have read. Wondering if the PRV is not working correctly. I can turn the side screw which I believe is bypassing the pressure setting (which hopefully doing that a couple of times on large system for just a few second didn't effect the pressure??). and that works. When I release that, I do hear a slower filling sound. Not sure if that is at the 15PSI level or it takes a few seconds for the valve to shut off completely again.

Any thoughts? I don't know what I'm doing 100% so it would be helpful have some additional guidance on what to try.

Jamie Hall

15 psi from the basement to a third floor radiator likely is not enough pressure -- as you have demonstrated to yourself by only getting air, not water, out of those upstairs radiators. Furthermore, the gauge may not be completely accurate -- they often aren't.

That said, you can still use the gauge, but to get enough water up there to get the air out you will need to bypass the pressure regulating valve. There may already be a bypass valve, but if not you can usually find some fittings which will help do that. Then you will purge each zone with ample water flow -- not just open the bleeders, but force water in one end and drain it out the other with a hose or somesuch. Then raise the cold pressure to about 20 psi (don't forget to check the expansion tank air pressure) and see.

Some photos of the piping arrangement may help us find fittings to do that purging.

timccarpenter

There is no way around the PRV. Here are a few pictures. Tangled web of pipes so hard to get a good shot. Is the 18-20psi so low that it would be a very slow fill when I'm trying to bleed the radiators?

STEVEusaPA

What kind of boiler do you have there with the plastic flue pipe?

mattmia2

Is the pressure reducing valve not connected to the domestic water system?

timccarpenter

- Lochinvar Knight for the PVC Exhaust
- Local code here doesn't allow the make up water line that is connected to the PRV to be connected to domestic water all of the time. You'll see it is connected via a washer supply line type hose

hot_rod

Often times when you try to flow backwards through a bib washer type of valve you can push the washer off the screw and it blocks or reduces flow. Use a ball valve where the hose connects.

You could also connect a hose to the house water pressure for a good volume flush. Just try not to exceed 30 psi as you purge. It helps to have two people, one regulating the fill, the other doing the purge, if you use house pressure

On your fill valve, if it has a metal hoop, that is how you put it into fast fill mode, lift it up. Yours may not?

timccarpenter

hot_rod, not sure I understand what you are saying with the bib washer type valve and ball valve. The hose connected is coming from the house water

hot_rod

The hose bib right above the fill valve, why do you need it,?
Just get a 1/2 npt to hose adapter and screw it into the ell. You have a ball valve right below.

When you flow backwards through a valve like that you can push the washer off the stem.

timccarpenter

I guess another follow up question. If I have someone on the valve side turn the open screw on the PRV (this seems to just open the valve to let water flow through) and then wait for the water to bleed out on the top radiator, don't I run the risk of increasing the overall system pressure? If this does happen, how do I decrease it back to a target of 20PSI cold?

hot_rod

Yes, that is why you want an accurate gauge. Boost to 20- 25 for purge, turn the screw up to decrease to 12 just before you finish the final purge. Shut the purge valve off observe and adjust to your final fill.

timccarpenter

Latest update. I had opened the valves for the connected house water. The PRV was not be set properly to 15 PSI so must have been slowly letting more water in. I had bled a radiator and then had to get on a conference call for 2hrs (left the make up water valves on). Went to try to bleed the radiator again and there was just a little air and then water shot out. I checked the pressure at the boiler and it was now at 50PSI. I tried to bleed off the extra pressure but it clearly was going to take some time. I went to the pressure relief valve and let off extra pressure until I got back to 20 PSI. At 20, I now again get little air and not water bleeding from the top radiator. I don't think my resting pressure should be more than 20 PSI, right (again 2 1/2 story house)? Now what. What am I doing wrong?

mattmia2

For starters you need to investigate why the relief valve didn't blow off before it got to 50 psi. What is the boiler and the valve rated pressure wise?

Are you sure you're looking at the right scale on the gauge?

timccarpenter

mattmia2 said:

Are you sure you're looking at the right scale on the gauge?

Think, actually, I was not reading the right scale. Looks like on the top scale at the bottom of the gauge, that is actual PSI....which is now probably too low..12ish PSI. The bottom of that bottom section is H2O feet...not sure what that is (that was what I read at 50 ...which looks would have been 20 PSI). Am I understanding this correctly? Maybe work my way back up to 20PSI at the max to get water up to that top radiator?

Also...why the relieve valve didn't go That valve is rated at 30 PSI

mattmia2

The feet markings were used to fill systems with open expansion tanks, you would fill it to the height of the tank to tell from the basement that the tank in the attic was filled. What it is doing on a mod con boiler, i have no idea.

Try bringing it up to the 20 psig. You probably need close to 20 psig cold fill to be able to push the water up to your highest radiators. If you don't keep it there and you have some tiny leaks like at valve packings, your top radiators may become air bound again. It looks like you have a larger expansion tank so if it is precharged to 20 psig you probably will stay below the 30 psig when it is hot.

timccarpenter

No idea what the expansion tank is charged to. I'll run the pressure up to 20 and we shall see. Appreciate the help here (I'd be lost without the forum!)

timccarpenter

Problem solved. Got pressure up to the third floor with about 18psi. Thanks for the help!