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loyal 04-06-2009 09:50 AM

Hydronic heat
I have an LP gas fired boiler, all copper piping, all base board heat.

Four zone control valves with four separate t-stats.

My question is how do I find a pressure leak in the system.

The leak is so slight that it may take weeks or months for the pressure

to drop below the cold pressure limit. But then I have to add water to bring

pressure up again. Needless to say, I have learned over the years how

to drain and re-set the expansion tank. The loss of pressure only

occurs when the boiler is running frequently due to extreme cold weather.

It's a nuisance and also bad for the system to keep adding new water.

So do I need to pressurize the system with air to somehow find the leak?

loyal 04-06-2009 08:06 PM

Must be some way to find the leak.:(

yuri 04-06-2009 08:44 PM

In extreme cold weather the boiler pressure will be at its highest and if you don't watch it carefully may reach the relief valve setting (sounds suspicious to me). If that valve is older, getting weak or has been dripping then that's your problem. If the expansion tank was full then it can pop the valve. You would be better off with a bladder expansion tank which can maintain a more even pressure and never needs draining. The only way to find a water leak is to see it.

loyal 04-06-2009 09:05 PM

Thanks for the reply Yuri.

I remember the first time the expansion tank got full.

The relief valve started letting water on the floor.

Just like you have described.:thumbsup:

I thought the relief valve was bad, so I replaced it.

Then I found out from a HVAC guy that the relief valve was opening up

because the expansion tank was full.

Anyways, so far I've checked all the bleeder valves for leakage with soap

water (don't know any other way). Replaced a few copper sweat joints

that looked green around the solder. Is it possible the seal between the

circulator pump motor and the pump impeller is leaking? I have noticed

water drops on the floor under the pump sometimes. This whole system

is about 15 years old.

kenmac 04-06-2009 09:37 PM


Originally Posted by loyal (Post 256052)
Is it possible the seal between the

circulator pump motor and the pump impeller is leaking?

Yes, a Few drops a day, hr, etc, will add up.. You don't have an auto water feed ??

yuri 04-06-2009 09:48 PM

A leaking shaft seal may be the culprit and should be taken care of. The one piece cartridge pumps by Taco, Bell and Gossett are less prone to leaks and have no spring couplers to break. Combined with a bladder tank you have a much better combination. You would have to cross reference the size of the pump with them. Adding water adds oxygen and contributes to corrosion in the system so a bladder tank is better. The air/oxygen gets directly absorbed into the water with those old archaic steel tanks and that is why they fill up.

Grampa Bud 04-06-2009 10:38 PM

Hi guy, You've said alot and not . Yes pressure leaks in a hydronic system can be a real problem to I.D., but since your system is older (15+ yrs) the system itself will most often do the detective work for you. You say you have all copper pipe and I'm assuming copper fittings so I would disregard the normal green (copper sulfate) corrosion that turns up at all your joints and anywhere the pipe or fittings have been sanded and/or treated with solder flux. DO look for any and all signs of Calcium buildup anywhere on the surface of all the parts of your system. THIS is the most predominant sign of a water and/or glycol leak on any system AND if water is getting out air is getting in. Another place people pass over is boiler drains/hose bibs. They don't leak much when they do but they do have rubber washers in them that do break down over time especially when they are subjected to 180-200*F for say 6 months and then sit cool for another six months. Check the bleeder on the airscoop that the hot output side of the boiler passes thru on its way to the system. Many times the tiny check valve in the bleeder will trap a small dirt or sand granule in its port and hold it slightly off its seat. I don't know whether you have the older overhead 15-30 gallon air/water expansion tank or the newer rubber bladder Extrol tank, but either should last many moons. The Extrol type should be prepressurized to system OPERATING pressure minus 2 lbs or say system pressure is 15 lbs -2 lbs = 13 lbs. If you have fin & tube radiators make sure you check the solder joints at both ends of all sections not just at the corners. If you have cast iron baseboard check the joints not only at the radiator ells, but also the squeese joints both hi and lo between the end panels and any intermediate panels. If there is a leak at one of those points it will usually show up as a small rust stain.

After all this do a pressure flush of the entire system with the expansion tank off or isolated. After all your circuits have run for fifteen minutes collectively (water only// no electricity) and the discharge point shows very few or no micro bubbles at all; turn the discharge valve off, turn the expansion tank on, and bring the system pressure up to the operating level. What you expect to see when the system is running wide open. If everything is good you should be golden for several years.

loyal 04-07-2009 09:04 AM

Great info!! Thanks you guys. Just what I was looking for!

I do have an auto feed, but I check boiler pressure every day, I try to keep

cold pressure at about 14-15. the hot pressure usually goes up to 20-22

at 180F high cut-off. I will definitely get a new bell & gosset pump. Thanks.

Also I DO have the calcium deposits around some joints!! I thought that might

be a problem, but my brother-in-law said no. So i will be replacing some

solder joints for sure:thumbsup: Thanks!

If you don't mind I would like to ask a few more ?'s

Three of my zone valves are the original ones. If only one zone was calling

for heat, and the valve on that zone was defective (stuck closed), and the

pump could not push water through, would the water be forced out of the

pump seal? Or would the pressure relief valve open?

I'm asking this because I'm thinking of getting one of those manifolds that

you guys use with the zone valves already installed. All the piping for this

system was done by the previous home owner. It works (except for the

leaks) but it's kind of a tangled mess of pipes, drain valves, shut-off valves

and zone valves floating in mid air mostly supported by the boiler itself.

If you guys think it's a good idea, I would like to install one of those

manifolds on the wall next to the boiler, and connect it up to the existing

zone piping with 3/4 in. or 1 in. pex tubing. The I would be rid of all the

old leaky valves and solder joints.

I suppose those manifolds are really costly though:confused1:

beenthere 04-07-2009 10:20 AM

If your getting a 6 to 7PSI increase.

Your tank may be undersized.

A 15 gallon tank. At best only has 1.33 cubic foot of space for water expansion.

Grampa Bud 04-07-2009 10:23 AM

I'm slightly cornfused here. IF you actually get your leaks stopped do you really want to disembowel your system just to make it look pretty? Just asking ! ! After I get my hands dirty I try to operate on the K.I.S.S. principle. For sure it can be done, but unless you have a great deal of prior knowledge of boiler/radiant controls you are going to run into many cold sleepless nights. 1. Zone manifolds whether feed or return do not generally come preassembled with a zone valve unless they are custom made for a particular purpose. That would be very EXPENSIVE.
2. If you want to zone anything think about your future maintenance for your system (there will be) and make sure there is a full port valve on EVERY branch of every manifold.
3. If you presently have leak free steel, or copper, or HEPEX lines LEAVE THEM ALONE.
Confucious say, "Boy who stick finger in works, most often get broken finger."
Also if you are thinking of incorporating HEPEX into your basgetti bowl let it be known that the parts and tools to install/use HEPEX are very EXPENSIVE, plus 3/4 or 1in HEPEX tubing is over a dollar a foot and unless you are going into radiant as a job, you will never recover the cost of the tools to work on the HEPEX.

Grampa Bud 04-07-2009 10:57 AM

An answer to your pressure leak question and pump seals or Press. relief valves. As long as you only have a low pressure hot water boiler, don't worry about blowing out "seals" or packing glands or solder joints. If such a leak happens it is for another reason. A normally operating boiler (hot water) can be expected to run for years @ 180-200F and 12-25 P.S.I. If a joint leaks, even a pissing leak, it is loose or a sealant is missing. If a seal, packing gland, valve, etc. leaks it is worn, or loose, or just old and decrepit like me. The same goes for the pressure relief valve, which by the way will last longer if it is NOT exercised periodiclly; just make sure you ONLY replace it with a 30 P.S.I. valve. I unfortunately have run across some dummies who have replaced a spent 30 P.S.I. valve with a water heater T & P valve rated for 100 P.S.I. and 125F and tried to operate the system

loyal 04-07-2009 12:57 PM

Thanks Gramps:thumbsup: I think I will replace the pump. I just found a replacement
B&G on the net. $206.00.

I used to have a HVAC guy come out every year for annual boiler maintenance. He replaced the hot surface ignitor every year because his
ohmmeter said the resistance was too high, took my old one with him of course, charged me $135.00 and left. That was his annual maintenance.

Eventually I had to find a new HVAC guy because the boiler stopped working.
Can't imagine why:mad:

After three service calls, putting in lots of new parts, (except the one
I suggested to them) and charging me big bucks, the boiler still did not work. So I gave up. What did I have to lose?? It was below zero outside!

I ordered a new flue pressure switch off the internet, shipped next day air.
Boiler working fine ever since. Now just need to fix leaks.:thumbup:

loyal 04-07-2009 01:42 PM

The pressure valve is a 30 P.S.I.

I took the old one in to HVAC and they sold me the right one.

I was only contemplating the manifold because I though it came with new

zone valves and shut-off valves already in place. I thought would be

easier than replacing my old valves and re-doing the solder joints.

But I'll take your word for it.:)

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