Slab floor radiant heat might have a leak

[TDKPE]

My in-laws’ summer house, which is walking distance from me (
 ) appears to have a leak in the hot water radiant system.  It was built in 1961 and is maybe 1500 SF, slab on grade, with what might be the original suitcase size boiler in an outside closet (no basement).  Single zone, with what I’m guessing is a balancing manifold in a hall closed with a bunch of valves with the knobs removed and copper tubing coming and going.

I check on it once a week or more, and found the heat not functioning, with the tiny pump running and making a weird pulsing sound (around 2 Hz).  Pilot was lit, but temperature gauge was low, and pressure gauge (single dual gauge unit) was down on the pin.  

I called the service guy with who they have a contract, and he said the water pressure was so low it cut out.  He let in some city water, did a quick check of systems, and all was well again.  Heat was still working the next day, and the indoor temp had come up to winter normal of 50F.

Check again today, and no heat (40F inside), pump motor was hot, and no pressure.  Not good.

I’ll have to ‘call the man’ again, but I’d like to know where the water is going, assuming it’s going somewhere.  If it’s leaking in the slab, how do they find it without breaking up the entire house slab and hoping for an early hit?  

I’d just like to know, though I’m not about to start tearing up their house looking for the leak.  How do they find a leak in a slab when no water is showing inside?

[barnowl]

A contractor in MA (Campanelli) built a ton of houses with that system back in the 60s and 70s.

They were a good design, and cheap to build... under cabinet boiler in the kitchen, with radiant tubing under slab.

However, once the copper sprung a leak, it was time to abandon the underfloor system, and replace it with fin tube baseboard.

Around the house, at the exterior walls. Depending on the size of the house, and number of zones, you'd have one loop, or two.

No, you do not have to fill the entire enclosure (in fact, you don't want to), but your contractor should do a heat loss calculation,

just like any other new installation, and install actual fin tube where called for. But the enclosure would be continuous, to either enclose fin tube, or piping.

https://www.google.com/search?biw=1315&b...CAc&uact=5

This is the simplest and least expensive option.

[TDKPE]

Yeah, my last couple of houses had fin tube, and the last house had what looked like the very same boiler.  Two zones.  Very simple. I even made changes myself, though I’m pretty good at soldering tube.

I hadn’t thought of retrofitting with fin tube.  I had thought that it would be a nightmare if/when the tubes go bad, back when they asked me to look at the house for them while they were considering buying it.  Same with hot and cold water pipes, also in the slab.

I warned them, but that’s cold comfort now, and being in their eighties, I’m certainly not going to say anything.  

At least they’re in Florida for the winter, and not up here freezing.  They get cold when it’s below 78F.  

[Bob10]

Yeah, my last couple of houses had fin tube, and the last house had what looked like the very same boiler.  Two zones.  Very simple. I even made changes myself, though I’m pretty good at soldering tube.

I hadn’t thought of retrofitting with fin tube.  I had thought that it would be a nightmare if/when the tubes go bad, back when they asked me to look at the house for them while they were considering buying it.  Same with hot and cold water pipes, also in the slab.

I warned them, but that’s cold comfort now, and being in their eighties, I’m certainly not going to say anything.  

At least they’re in Florida for the winter, and not up here freezing.  They get cold when it’s below 78F.  

any attic space to house a forced air unit?

[TDKPE]

any attic space to house a forced air unit?

That’s a possibility.  Very tiny attic, though.  Half the house has cathedral ceilings, the other has shallow attic.  But with the cathedral ceiling, there’s a ‘beam’ down the middle, and that could be built out with duct and registers and made to look (almost) like it belongs.  Good thought.

As to water around the foundation, yes, lots of it, but it’s white and cold.  


Sorry; I couldn’t resist.

There is an automatic feed valve with “12 psi” stamped on it, and it looks pretty new.  That’s followed by a backflow preventer (check valve), and those two valves are flanked by ball valves.  

The incoming feed water ball valve is off.  I don’t know if it should be, but I kind of don’t think so.  The automatic regulator does seem to work, though, as I have to lift the manual hoop handle to add water once it’s higher than some value, though I haven’t messed with it enough to know where it shuts off on its own.  Should be 12 psi or thereabouts, but I’ll find out tomorrow.

I just got back from their house, and the pressure was down a little again, so I jacked it back to 25 psi. I’ll go back tomorrow and see where it is then.  40F in the house and it takes two days to warm up, so I want to keep it running as cold weather is on the way.

I also don’t want to call the service company until I actually know something.  No point in them adding water and telling me to let them know what happens.  I’m already doing that.

[jteneyck]

In normal operation, the water supply valve should be on.  The downstream regulator will lower the pressure to 12 psi as it enters the boiler loop.  There must be an expansion tank somewhere, too.  The modern type are no bigger than a small propane canister like on an outdoor grill, and have an internal bladder.  They are back filled to 12 psi air pressure.  With this arrangement the system will always have at least 12 psi, even if there is a small leak.  It would take a leak larger than the supply regulator can keep up with for the pressure to drop below 12 psi. 

I don't know why the water supply valve is shut off unless the tech. decided that was better than having a flood somewhere.  But if he knew there was a leak you think he would have told you so.  

If it comes to a new heating system can you piggyback into the central AC system by adding a heat exchanger from the boiler or a heat pump?  If there is no central AC then how about a split mini system and heat pump?  

John

[brianwelch]

Copper and concrete do not play well in the long run...As is stated above, abandoning the existing in slab system is probably a prudent move. Even if you locate the current leak and repair, it will most likely a short term solution. In addition, moisture from the leaks such as what you are experiencing often result in termite damage. 
There are 10's of thousands of local homes built in the 50's by a developer by the name of Levitt here in the PA/NJ area...
Very common occurence due to the in-floor radiant heat system...

[TDKPE]

There are 10's of thousands of local homes built in the 50's by a developer by the name of Levitt here in the PA/NJ area...

Of Long Island’s Levittown fame?

“There’s a green one, there’s a red one . . . And they’re all made out of ticky-tacky, and they all look just the same.“ 

[Roly]

They use a thermal imaging camera to locate the leak.   You might have one at work you could borrow.   But I will go with the others, it is just the first one. There will probably be more to follow, just a matter of when.  Roly

[Stwood_]

Any unusual wetness outside around the foundation?