Leaking Hot water baseboard system?

genericnj

I have a 2 zone gas-fired hot water baseboard system with a single circulator pump and two zone valves. Last year some of you helped me to update the system with new purge valve, vents, feeder and backflow preventer, and replace a seized circulator pump - it has been working fine since then, however something concerning is that this season i started to hear a gurgling sound in the upstairs baseboards. I checked the pressure on the boiler using a watts 2 1/2 in hose gauge - and it showed 0 psi at hot and cold ... i thought my gauge must be faulty since there is heat and aside from the gurgling no other issues... so i bought another gauge at lowes and same reading of 0 psi...

So i started to add water by turning the feed valve on, it took a long while (couple minutes) of water going in before the gauge started to go up and eventually hit 12psi.

- The system is 1985ish so not very new, boiler is a Burnham, I checked while boiler is burning and no steam appears to come out of the chimney, no hissing of any kind at boiler, so i am assuming the boiler is not cracked.

- I do not see any leaking from any of the baseboards. Some of the system is under a SLAB foundation and I live in the NorthEast so winters are brutal here, but I always have the system on in winter.

- I checked the expansion tank and it seems fine, when i knock on it, it sounds light and echoy throughout half the tank.

Since this is a sealed system I did not expect any loss of water, especially that much water. I have it refilled and it is working fine, just as before, I also purged the air at the upstairs baseboards and it did spit out some air especially in the room where i heard most gurgling.

My biggest concern is what if there is a leak somewhere underneath the slab and thats what is causing the water loss, but I have no signs of it or any way to check for it... any thoughts or pointers?

many thanks in advance!

Jon_blaney

What kind of pipe is under the slab and how long has it been there? I would look for hot spots in the slab. If the slab is exposed, try running your hand along the pipe's path.

genericnj

I assume it is all copper as the pipes coming from the slab to the baseboards are copper and so is the pipe going into the slab from boiler. I do not know the paths of the pipes under the slab though, I only know where they come out for the radiators and can 'assume' where they go from there, but in some cases no idea... The slab is not exposed, except for the utility closet where the boiler is. The rest of the slab is covered by fairly thick hardwood flooring.

I havent felt any spots that feel much warmer than others to be honest, but the floor is almost an inch thick so it may insulate any heat...

A

Jon_blaney said:

What kind of pipe is under the slab and how long has it been there? I would look for hot spots in the slab. If the slab is exposed, try running your hand along the pipe's path.

EBEBRATT-Ed

walk around with bare feet you might find it. or get a cat they will lay down on the warmest spot

genericnj

so mine starts 12psi cold and gets to just under 15psi right when the firing finishes. The boiler gauge is long dead and is in a spot that i cannot easily access to replace it, so I am only going by the drain hose attachment, and I have tested 3 different gauges to make sure I'm not using a faulty one. The worrying thing is that I was at 12 psi cold about a year ago when I refilled it then, the fill valve has been off the whole time so no new water went in, but the boiler went all way to 0 psi and I had to refill what was probably around 2-3 gallons of water... I'm just worried because that water had to have gone somewhere, but I have no symptoms of it leaving the boiler at all ... No steam out of chimney, no drips anywhere, no wet ceilings from 2nd floor, nothing noticeable on walls or floor or 1st floor. Which is what left me wondering what could be happening with the pipes I cannot see that are in the slab

genericnj

hm it felt like a lot of water to add - it literally ran for about 2 minutes before the gauge started to climb to 12 psi and I could hear the water rushing in that whole time so it definitely took a lot of additional water... I did not check the gauge throughout the year so no idea if it gradually dropped to 0psi, but when I left it last year it was at a perfect 12 psi when cold...

I figure if it was getting too high pressure when hot then the blow off valve would get triggered, and I replaced that last year and tested so definitely works ... but who knows... I really do hope you're right and it is not an actual leak...

mattmia2

If you drained and refilled the system then there would be air dissolved in that water that needs to get out and you would have to add more water to replace that air. There could be very small leaks at things like valve packing that are too small to see. a couple gallons over a year isn't enough to worry about but keep checking it until you figure out if/how much it is losing.

Peter_26

When is the last time the expansion tank has been replaced, if ever?

genericnj

Peter_26 said:

When is the last time the expansion tank has been replaced, if ever?

It has never been replaced Peter - however when i tap on it, about half the tank appears to sound hollow and air filled as it should and the part where water enters sounds more solid - the tank also does not seem waterlogged as it is pretty 'light' when i tap on it the whole thing shakes a bit. Also the pressure differential cold vs hot appears to be only 3 psi or so, which i believe would be much higher if the tank was faulty.

I have been monitoring the pressure and it appears to be losing about 0.5 psi each day since i added water - I also sealed the vents to make sure nothing leaves the system while i have been watching it. I have been checking psi right after firing is done and also when the boiler had chance to cool for 1 hr. in both cases the pressure appears about 0.5 psi dropping each day since I had added water a couple days ago.

Also, I looked everywhere on the first floor for any hot spots around the floor, but i do not see any, walked around barefoot, moved furniture out of way etc... nothing seems to show any areas that are unusually warmer - only areas that are slightly warmer are right next to the actual baseboards and they are evenly warmer with the run of the baseboard...

genericnj

Do any of you recommend either of these products? I am still losing very small amount of pressure, not sure where the leak is but at this point i'm considering trying one or both of these:
https://www.supplyhouse.com/Hercules-30213-12-oz-Base-Hit-II-Sealant
or
https://www.supplyhouse.com/Hercules-30-115-1-qt-Boiler-Liquid-4101000-p

The first option seems to fix leaks in the piping and 2nd seems to focus on boiler leaks - any drawback in using both of these? or either one i should try first?

SuperTech

The tap test for the expansion tank is not a reliable or accurate way to test the tank and it can be deceiving. The only way to test it is to check the air pressure with a gauge when you don't have any water pressure on the tank. 

I wouldn't be surprised if you had a leak under the slab. I've seen it happen several times. Is the pipes that are under the slab only for the lowest level? You can isolate it then.  I have seen some raised ranch houses where the piping from the boiler to all the zones were run under the slab for some stupid reason. 

STEAM DOCTOR

You can test the expansion tank by pushing the Schrader valve and see if water comes out or air. 

genericnj

SuperTech said:

The tap test for the expansion tank is not a reliable or accurate way to test the tank and it can be deceiving. The only way to test it is to check the air pressure with a gauge when you don't have any water pressure on the tank. 

I wouldn't be surprised if you had a leak under the slab. I've seen it happen several times. Is the pipes that are under the slab only for the lowest level? You can isolate it then.  I have seen some raised ranch houses where the piping from the boiler to all the zones were run under the slab for some stupid reason. 

The piping under slab only serves the lower level zone .. I suppose I could try shutting off one zone with the valves but the leak seems to be sooo small that it would take me a couple days minimum to test and it is too cold to leave one zone with no heat
Maybe when we have a few warm days like we had just now .. so i would shut off the lower zone and let the system run as usual and then see if the pressure is still dropping with just the upper zone in operation right?

STEAM DOCTOR said:

You can test the expansion tank by pushing the Schrader valve and see if water comes out or air. 

I just tried and air comes out of the valve just like from a bicycle tire -- only did for split second since dont want to let air out of it..

mattmia2

If it takes a couple days to discover that it is leaking then this can wait until spring, just keep the auto feeder on.

genericnj

Looks like i accidentally deleted my reply while trying to edit it ...

SuperTech said:

The tap test for the expansion tank is not a reliable or accurate way to test the tank and it can be deceiving. The only way to test it is to check the air pressure with a gauge when you don't have any water pressure on the tank. 

I wouldn't be surprised if you had a leak under the slab. I've seen it happen several times. Is the pipes that are under the slab only for the lowest level? You can isolate it then.  I have seen some raised ranch houses where the piping from the boiler to all the zones were run under the slab for some stupid reason. 

The lower zone goes under the slab only, upper zone does not -- once we have a few warm days I could try to test by using the valves to shut off the lower zone and then run the system as usual for a couple days and check to see if pressure has dropped?

STEAM DOCTOR said:

You can test the expansion tank by pushing the Schrader valve and see if water comes out or air. 

tested but only air comes out - did it for a split second only

genericnj

mattmia2 said:

If it takes a couple days to discover that it is leaking then this can wait until spring, just keep the auto feeder on.

I'm tempted to try the Hercules Base Hit II people in the reviews seem to rave about it helping with small leaks and would rather not let it get worse ... i have no idea how long this leak has been going on to be honest ... last year the pump died after I owned the house for 2 years, it may have died because the pressure was low from leaking, who knows...

mattmia2

You are much more likely to cause problems with the "stop leak" than a gallon or so of water a week will cause, at lest over a couple months. If you let it go for years it could lead to short life of things. If the PRV is set up right it should keep pressure on the system. Loss of pressure could damage the circualtor but it more than likely just died of old age.