Possible leaking in copper radiant floor?

[1634j]

I've owned my present home since 1991, it is now ~60 yr. old, ~1,000 sf slab on grade with the original copper in-slab radiant heating. In 2007 a new Buderus condensing boiler was installed along with a Buderus indirect hot water tank, all new above slab piping, manifolds, individual loop valves and pressure gauges were installed, the contractor air pressure tested all the in-slab loops for 48 hr., no pressure drop in the loops. The new boiler operates as a closed system with the autofill valve closed, the contractor set the system pressure at 20 psi, if pressure drops to ~12 psi the boiler will shut down. Some time after initial installation a very slow loss of pressure was evident, working with the contractor one of the two loops in the utility room was identified as a problem, a leak detection specialist was not able to find it with above slab equipment, he calculated the loss from the loop at .0172 oz./min., since the utility room has a second loop plus heat from exposed piping above the slab, we just agreed to keep that one leaking loop closed. Since that time there has continued to be very slow pressure drop somewhere in the system. When the boiler begins a heating cycle there is a 1+ psi surge on the loop gauges. In the heating season I may need to refill the system to 20 psi once a month, in the non-heating months once every three months. There is never any above-slab water leaking evident. Questions:
1. With condensing boilers and indirect water heaters, is there any other possible cause for this pressure drop in the copper piping other than a leak somewhere in the copper distribution piping?
2. Assuming there may be a very small leak(s) somewhere, I have read about epoxy lining, it has drawbacks as a possible "repair". I have found an English company fernox.com advertising leak sealer products "ideal for reducing pressure loss from sealed systems". Any comments about the Fernox product, or do you now of any other similar USA products that might be appropriate to try?
3. Other than abandoning the existing in-slab piping, any other suggestions?
Thank you.

[beenthere]

Not familiar with those products.

Just wondering why you need 20PSIG on a slab system, when the boiler is above the heating loops.

[crmont]

Not familiar with those products.

Just wondering why you need 20PSIG on a slab system, when the boiler is above the heating loops.

Exactly what I was thinking. Run that sucker just slightly positive.

[1634j]

Just wondering why you need 20PSIG on a slab system, when the boiler is above the heating loops.

When the crew intially installed the boiler, they set it at a lower psi (don't recall exactly what number). When I first had a low pressure shutdown, the owner/sales man came out and one thing he did was re-set the pressure at 20, wrote a "20 psi" note on part of the system so his techs would know in the future. Don't recall exactly what his reason was. Also, fwiw, once early on they replaced the expansion tank ... (?)

[swaskewicz]

Try to find someone with a thermal camera, and have the system scanned.
If there's a leak, he'll find it...

[DaveCR]

From my point of view, 60 years for copper-in-slab is pretty amazing considering systems in this area began to fail at the 25 year mark. I believe this is the beginning of the end of your radiant system.

[Kevin O'Neill]

Try to find someone with a thermal camera, and have the system scanned.
If there's a leak, he'll find it...

I agree with the thermal camera idea. We have one, and it is amazing what it will see.

The have dropped a lot in price the last 2 years.

[beenthere]

When the crew intially installed the boiler, they set it at a lower psi (don't recall exactly what number). When I first had a low pressure shutdown, the owner/sales man came out and one thing he did was re-set the pressure at 20, wrote a "20 psi" note on part of the system so his techs would know in the future. Don't recall exactly what his reason was. Also, fwiw, once early on they replaced the expansion tank ... (?)

Running a 60 year old slab at 20 PSIG is a recipe for trouble.

[REP]

Say goodbye to your in floor heating.Its one loop now and at least 4-5 in the coming year if not more.
Cheapest way out will be up against the wall baseboard radiation.

[1634j]

Running a 60 year old slab at 20 PSIG is a recipe for trouble.

Could you please elaborate? (The contractor who did the installation and followup was recommended to me by the local Buderus distributor.)

[coolwhip]

An infared thermometer works for me. You can follow the loops in the floor and find the area with a large diameter of heat. break up the slab in that area and repair the leak. Ive done it dozens of times.

If its really tough, there are companies that will find the exact location useing an ultra sonic detection method. Usually this will happen on a sand foundation where the water is going down in the ground and not pooling.

[1634j]

Say goodbye to your in floor heating.Its one loop now and at least 4-5 in the coming year if not more.
Cheapest way out will be up against the wall baseboard radiation.

Well, if worst case would mean abandoning the existing in-slab piping ....

Upper midwest winters here, domestic water piping is in the slab also. Kitchen sink is on an outside wall, exterior hose bibb stubs up and out next to kitchen sink piping, toilet is adjacent to outside wall. I wonder if I'd need to be concerned about freezing if the slab was not heated, therefore worst case may be a new radiant piping system on top of the slab ... ?

[REP]

Well, if worst case would mean abandoning the existing in-slab piping ....

Upper midwest winters here, domestic water piping is in the slab also. Kitchen sink is on an outside wall, exterior hose bibb stubs up and out next to kitchen sink piping, toilet is adjacent to outside wall. I wonder if I'd need to be concerned about freezing if the slab was not heated, therefore worst case may be a new radiant piping system on top of the slab ... ?
If that is an option then I'd start pricing it out now.
The problem is that the lime and other caustic chemicals in the cement and the rushing water at a high pressure have eaten the copper pipe thats incased in the cement.Plus the normal expansion and contraction of heated copper pipe rubbing against the concrete.
In my experience,I have run into this problem 3 times.
Twice I tried to repair the leak only to have one or more loops in system spring leaks durning that heating season.The last time I just installed baseboard radiation.

[Kevin O'Neill]

You could install tubing on top of the floor and pour lightweight grout/cement over top of it.

[REP]

You could install tubing on top of the floor and pour lightweight grout/cement over top of it.
I love in floor htg and if it were my house I would look at ways to save it.
What you suggest is possible but its a big job.The floor will have to come up 1" to 1 1/4".
All baseboard molding has to be yanked,all doors will have to be worked on in order to fit the frames.
You'll never have to do it again as pex will not fail like the copper is doing and installing baseboard radiation is a big job too.So I guess its 6 of one and a half dozen of the other.

[1634j]

Update -

Correspondence from a sealer company: introducing a sealer additive into the boiler's circulating system is probably unacceptable to Buderus.

Regarding spot identification/repair of leaks, I'm not favoring this approach because of the age of the in-slab piping. The option to install a new overlaid dry system seems worth pricing out, currently waiting for a Raupanel estimate.

Another concept (to avoid total abandonment of the slab piping) -

In order to protect the Buderus boiler's aluminum heat exchanger from new make up water, what about isolating the boiler from the floor slab loops by installing an additional heat exchanger along the distribution piping route? Perhaps a sealer could be introduced then to help pressure loss. If the additional heat exchanger should have problems because of fresh water being introduced, it would be far less costly to replace than an entire Buderus boiler. Thanks for any comments.

[1634j]

Update - My boiler contractor determined that every in-slab copper loop now has some degree of pressure loss, probably pinhole leaking. He explored the option to isolate the loops from the boiler with an additional heat exchanger, etc. with sealer product, bottom line as expected, no one thinks this is a dependable long term solution. The boiler contractor is currently pricing a Raupanel system. However ...

My boiler contractor also mentioned an alternate heating source of running lines from the boiler up to my attic mounted Unico air handler (now just used for cooling) and adding a hot water coil segment to the Unico, he says there are antifreeze products that could be used in the Buderus boiler, at first I didn't think much of this concept because of my concern for a cold-feeling slab and possible freezing of domestic water in the slab at the building entry and kitchen (both along the exterior wall). Maybe I'm overconcerned about freezing? My carpeted and floating Pergo rooms presently never feel warm or cold, maybe if I changed the ceramic tile bath and foyer to a floating floor (engineered hardwood) I wouldn't notice the cold slab underneath? The Unico has well insulated high velocity mini-duct distribution, runs a bit noisier than conventional forced air. Re. the copper in the slab, maybe the loops could all be drained and valves shut but not be totally abandoned in case I ever needed an emergency backup ... ? Any comments are appreciated.

[REP]

Update - My boiler contractor determined that every in-slab copper loop now has some degree of pressure loss, probably pinhole leaking. He explored the option to isolate the loops from the boiler with an additional heat exchanger, etc. with sealer product, bottom line as expected, no one thinks this is a dependable long term solution. The boiler contractor is currently pricing a Raupanel system. However ...

My boiler contractor also mentioned an alternate heating source of running lines from the boiler up to my attic mounted Unico air handler (now just used for cooling) and adding a hot water coil segment to the Unico, he says there are antifreeze products that could be used in the Buderus boiler, at first I didn't think much of this concept because of my concern for a cold-feeling slab and possible freezing of domestic water in the slab at the building entry and kitchen (both along the exterior wall). Maybe I'm overconcerned about freezing? My carpeted and floating Pergo rooms presently never feel warm or cold, maybe if I changed the ceramic tile bath and foyer to a floating floor (engineered hardwood) I wouldn't notice the cold slab underneath? The Unico has well insulated high velocity mini-duct distribution, runs a bit noisier than conventional forced air. Re. the copper in the slab, maybe the loops could all be drained and valves shut but not be totally abandoned in case I ever needed an emergency backup ... ? Any comments are appreciated.
If designed properly what your guy is perposing will work.
Another choice would be RADIANT baseboard.It is a cousin of radiant floor heating.There are even radiant wall panels for large rooms.
Its just a thought and another choice for you.

[1634j]

"If designed properly .... "

What particular design concerns?

fyi I just checked the Unico M1218 installation manual against the unit in my attic: there is already a housing area space for a heating coil exactly as shown in the manual, I'm assuming installing a coil in the unit itself would be straightforward. Running water lines from/to the boiler should be doable also.

Regarding radiant baseboard and/or wall panels, my contractor and I have discussed: perhaps one or two in the utility room but probably not in the rest of the house (space and routing complications).

Thanks.

[REP]

"If designed properly .... "

What particular design concerns?

fyi I just checked the Unico M1218 installation manual against the unit in my attic: there is already a housing area space for a heating coil exactly as shown in the manual, I'm assuming installing a coil in the unit itself would be straightforward. Running water lines from/to the boiler should be doable also.

Regarding radiant baseboard and/or wall panels, my contractor and I have discussed: perhaps one or two in the utility room but probably not in the rest of the house (space and routing complications).

Thanks.
Did not know what coil info you had already.Also sometimes there are areas in the house (hallways,staircases etc) that are not installed with supplies with a unico type unit so the coil has to be able to warm the whole house and all areas.

[1634j]

"... sometimes there are areas in the house (hallways,staircases etc) that are not installed with supplies with a unico type unit so the coil has to be able to warm the whole house and all areas."

Single story, all rooms except small entry foyer have supply outlets, return grille is in central hall, so I'm not concerned with even distribution (cooling works fine). More concerned about having a cold feeling floor, possible freeze problems at slab perimeter.

[hvac248]

An infared thermometer works for me. You can follow the loops in the floor and find the area with a large diameter of heat. break up the slab in that area and repair the leak. Ive done it dozens of times.

If its really tough, there are companies that will find the exact location useing an ultra sonic detection method. Usually this will happen on a sand foundation where the water is going down in the ground and not pooling.

Or look were the cat sleeps.LOL

[heaterman]

How large is the home? How many levels? Where is the boiler located (center, outside wall area?)?

[1634j]

How large is the home? How many levels? Where is the boiler located (center, outside wall area?)?

Single story slab-on-grade. Main house is 841 SF, gable roof attic space is good (Unico is up there, easy to service, attic access has pull down stair). Sandwiched between the main house and the attached garage is the 122 SF utility room, the Buderus boiler is wall mounted on the garage wall (concrete block back up). Distance from boiler to the Unico is about 16' horizontal, vertical elevation change about 8'. Running supply/return piping from the boiler to the Unico up through the utility attic over to the main house attic would be no problem for a pro.

[1634j]

Update once again -

Well, seems like I explored every option and there are no good long term and future re-sale solutions other than abandon the existing in-floor copper and install a dry system overlay. Raupanel appears to be the most attractive product in terms of performance, shallow depth. Made the downpayment today. The expense is unfortunate, this too will pass.

Waiting for the contractor to confirm materials delivery so we can firm up install start.

Any comments related to the Raupanel upcoming work are appreciated. Thanks to all.