Can't refill my gas boiler hydronic radiator system after draining for repair

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Old 02-13-13, 10:37 AM
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Can't refill my gas boiler hydronic radiator system after draining for repair


Hi all,

Not sure how Posts/Threads work, so just added this here hoping someone looking at the original Post may have ideas for me. Thanks.

I had to drain the system (older Burnham boiler, cast iron radiators, older house) to replace the B & G #100 circulator pump bearing/impeller assembly because of a leak (spring coupler went first). All that went fine and no leaks, but after 2-3 hours of supply water valve to boiler full on (an increasing screw setting for pressure limit valve from 12 to about 15 psi), and could hear water flowing, I could not get any into even the first floor radiators, and no sound at any of the open bleeder valves. Then thinking that I needed to heat up the water to increase pressure, I still only had 5-10 psi reading in the boiler, and only one fist floor radiator nearest the boiler got hot, with the only supply pipes (big old 3-4 inch iron pipes) in basement getting hot but return only lukewarm and all other radiators cold.

So I think I probably have a leak in the pipe (supply or return) under that room, but have no access to that space: bricked base in with my basement foundation on the house side. Tried to listen for sound of leak, but can't tell. I know water is flowing into the system and no other leaks anywhere, and everything else is either visible or would show up in house.

Does this sound like a leak in the pipes that did get hot, including radiator eventually, or do I just have to keep filling for many more hours? The heat of the inflow/outflow pipes at that one radiator made it clear that the boiler was circulating or warming up only to that one, and boiler would cycle off after about 5-10 min, with some air/water belching. And I kept the water valves to the system open to be sure it had supply.

And if it is a leak and I have no way of getting to it to repair (unless I cut into/remove some of the floor over those pipes?), I think I would have to cut and cap both the supply and return pipe just inside my basement wall (after draining the system again, or at least to the level of those pipes). There is a second radiator in that room, so I can go with out the one.

Thanks in advance for any input.

Jim
 
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Old 02-13-13, 12:54 PM
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ps. forgot to mention that my water supply line to boiler is 1/2" copper not 3/4

Smaller pipe may be causing longer fill time....thanks
 
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Old 02-13-13, 01:24 PM
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No, it should not take hours...

If you hear water running and don't see any water, I'm afraid that you may in fact have a leak.

Has the system been turned off during cold weather?
 
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Old 02-14-13, 04:59 AM
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Thanks. System has been on, but we were not using 3rd floor, so I closed those valves but left attic door open and assume those 3 radiators and lines did not freeze. Winter has not been too bad/cold here except for a couple of spells.

With system hot, I can trace the point in the basement supply line that the hot water reaches, and the last 1 or 2 vertical supply pipes that got hot - that is, about 3-4 verticals got hot from boiler out (on the one side of house) and I think same on other (will recheck this...it got late last night). But only the return lines closer to the boiler were fully hot, as was the 1-2 radiators first floor closest.

So I am thinking that the last hot vertical supply pipe should indicate the leak? Or is it that the leak can be earlier and it is just not allowing system water above a certain height from boiler? And let's say is it is one of the long verticals (maybe 20-24 feet) to attic, is the fix to empty system (or lowest point for those 2 pipes), cut out near basement feeders and at radiator, and run copper up along side it to tie in or ??

Thanks for input.
 
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Old 02-14-13, 07:02 AM
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I wouldn't trust a hot/cold pipe to indicate which has a leak.

Reason being that you could ALSO have a circuit that is blocked by air in the pipe and those would also possibly be a cool pipe... in other words, not a DEFINITE test. You don't want to go cutting and replacing pipes for no reason.

If you were running that much water, wouldn't you have 'liquid evidence' of a leak?
 
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Old 02-14-13, 07:40 AM
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Good point. So in a closed loop going to 3rd floor, that trapped air cannot be pushed out/overcome by the booster pump? So is it possible that alot of air in most of the loops cannot be overcome by the supply water pressure and booster pump running?

And yes, no visible water anywhere. Only 2 possible places are 1) the space under the radiator closest to boiler that I mentioned in my original posting (space has no access, and probably just dirt below - it is a side "sunroom"), or 2) a crawl space under the kitchen baseboard radiator unit (added during a remodel).

I guess I will have to open up that space access panel to check for water.
 
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Old 02-14-13, 09:12 AM
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Good point. So in a closed loop going to 3rd floor, that trapped air cannot be pushed out/overcome by the booster pump? So is it possible that alot of air in most of the loops cannot be overcome by the supply water pressure and booster pump running?
Correct... the pump can't develop enough 'head' pressure to move an air bubble downhill. Think about the last time you tried to 'sink a beach ball'.

SUPPLY WATER PRESSURE will be high enough to push the air out, but you have to be able to manipulate the proper valves at the boiler in order to 'route' the water and force it to go up into the zone...

Lastly, since you've mentioned a 3rd story... when the boiler is COLD, you need to have a MINIMUM STATIC PSI on the boiler gauge of at LEAST 17 PSI in order to properly circulate water through the 3rd floor pipes.
 
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Old 02-14-13, 11:57 AM
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System running and hot all 3 floors. Got enough pressure to air out by 1) screwing in pressure limit "valve" to allow higher boiler supply pressure, and 2) connected hose from laundry facet to boiler drain valve (garden hose plus female-female washer hose) and ran in 20% force (and I think my house main being old cast iron is only giving me about 40-45 psi) hot water - have heard the big cautions about cold water into a hot cast iron boiler!). Bled system from bottom up and "we're cookin' with gas" now!

Finally, glad about your last point because the system is now at 20 psi hot (and I assume it will drop to 16-17 cold), which takes care of the 35 feet from boiler to 3rd floor radiators. Is the formula 5 psi (cold) for every 10 feet above boiler?

Thanks alot NJ Trooper!
 
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Old 02-14-13, 02:00 PM
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ps. after running for a couple of hours, hot boiler pressure is 22 psi...should I do something to reduce pressure now, wait to see if at cold it gets down to 17 psi (not sure I will let it chill until a couple of days from now given 4 days of down time/house in the 50's), or is 22 psi within boiler specs? I will check the spec plate on the boiler, but suspect that if the safety release valve is set at 30, we are probably fine.

thanks again!
 
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Old 02-14-13, 02:36 PM
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Is the formula 5 psi (cold) for every 10 feet above boiler?
Probably close enough for 'gummint' work... the exact formula would be:

HEIGHT X 0.431 + 4

35 X 0.431 + 4 = 17

The 4 PSI added is to insure that there is always some positive pressure at the tippy-top of the system. Even if it dropped to 16 you would still be OK.

Remember too that boiler pressure gauges are lying, evil devices.

http://www.doityourself.com/forum/bo...ure-gauge.html

hot boiler pressure is 22 psi...should I do something to reduce pressure now
No.

wait to see if at cold it gets down to 17 psi
Yes.

(not sure I will let it chill until a couple of days from now given 4 days of down time/house in the 50's)
Let the house warm up.

is 22 psi within boiler specs?
Yes.

suspect that if the safety release valve is set at 30, we are probably fine.
Correct.

If the pressure approaches 27 PSI start thinking about letting a little off. You want to operate the system at no more than 10% below the relief valve setting of 30.
 
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Old 02-14-13, 02:45 PM
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ps. forgot to mention that my water supply line to boiler is 1/2" copper not 3/4

Smaller pipe may be causing longer fill time
Perhaps the fill valve strainer screen is partially plugged?

===========================================

Can we talk about the expansion tank since it affects the pressure 'swing' within the system?

I'm guessing that yours is the steel variety in the joists above the boiler, yes?

If the expansion tank is partially waterlogged, you will see a wider swing in pressure from cold to hot boiler. With a waterlogged tank, you may be at 17 cold, and swing higher than 27 hot. If you notice this happening, we can talk about how to drain the expansion tank and get the air cushion back in.

Is there a shutoff valve on the line going to the tank?
 
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Old 02-14-13, 07:02 PM
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Will check out the how to test actual boiler pressure site soon. I suppose rigging a pressure apparatus to the boiler drain valve is one way. I know the temp gauge on the boiler is gone - shows 140 F when cold, so not sure if this indicates that the pressure reading is also predictably wrong. So will just monitor the cold to hot pressure change and enjoy the heat in time for a pretty cold weekend.

Yes, I have a steel barrel expansion tank above boiler in the floor joists with valves to boiler and outflow, and I keep that half full. Thanks for that reminder. It did start to spring some underbelly leaks last year, and a local welder plated some for me and PC7 epoxy did the rest.

Finally, thanks everyone - I realize now that there may be multiple thread responders with NJ Trooper moderator being one of you.
 
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