Leak in slab!!

Grumpy

3800 sq.ft. ranch, slab on grade, three zones baseboard hot water system with all loops and mains in the slab. System is on well water feed and pressure regulator feed line is colder than a well digger's bum! Obviously feeding water at a constant rate. Plugged off all vents, removed expansion tank, plugged relief valve and then pressurized system to 50psi with bypass valve, then closed off water feed line. System dropped pressure like a rock. Last time this occurred (5 yrs ago) an oldtimer found the leak using a broom handle up against his ear. He's worm food now, so it has become my task to find and repair this mess. No visible signs of water inside, no hot spots anywhere, nothing visible on exterior of slab. Short of calling the infrared camera folks in from 70 miles away and an estimated $1500 fee for their services, I'm looking for some insight and ideas. Anyone have any?

Earthfire

have you

tried a couple of infrared thermometers?(Raytec?)Might be able to get a temp. delta between the leak and none leaking pipe. Know anybody with the water company? They usually have sonic equipment to locate leaks or know of a good leak locator service.

[Deleted User]

compressed air and a medical stethiscope

bring your kneepads..

hr

After watching

my Leakbuster guy on three seperate jobs now, it seems the device that ALWAYS work is the listening device he has.

He starts with inert gas and a sniffer, heat seeking equipment, then if all else fails the earphones.

I think the first two are much faster methods, but tube at the bottom of a slab is tough to smell or heat seek accurately.

It is a very slow process. He works a grid pattern in the room or driveway. .

On the last one we ran a very slow flow of water and he injected nitrogen to cause the bubbleing sound that the head set picked up. The room has to be very quiet, hense the nitrogen bottle instead of a compressor.

I tried it a few times, with borrowed equipment, it really helps to have an operator with experience. I never did hear the sounds he did. And he has always pinpointed the leak, or leaks!

It usually an all day process, even on a small residental slab.

Having the trick equipment is a big plus. Knowing how to use it is the key

Good luck! And I second the knee pads. Buy a comfortable gel filled set, you may be down there awhile.

hot rod

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Grumpy

Tried finding it with my Raytech thermometers. No luck that way. I used a stethiscope too -ditto on the results. I will give the delta T idea a good look tomorrow. I'm working up a price on repiping this system using pex runs in the attic and down the exterior walls to the baseboard units. Since the house is on well water, the water company is unwilling to get involved with equipment or even recommendations for assistance (nice guys) They said they have "in-house" people that do their detection work.

Grumpy

I'll probably need the knee pads for all the praying I'll be doing, "Dear Lord get me out of this misery!"

Mark_25

Is it really that common to have a slab leak? I've never heard of anybody that had one before using pex.

Grumpy

Never said it was pex, Mark. Sometimes we still have to work on these 40 year old copper systems in the slab.

Mark_25

Ah! My bad. The OL' expansion/contraction copper thing...

hr

Copper has

a fairly reasonable track record in slabs. The biggest unknown is the reaction with the concrete ingrediants, especially when wet.

The soil type below the slab (as most tube touches the subgrade somewhere) and the expansion and movement of the slab. Some feel the fly ash used in the concrete mix and the cinders used as backfill or concrete blends was most at fault in those homes. I'd tend to agree.

I think this combo doomed the Levit homes. But really is a 40- 50 life expectancy really that bad

hot rod

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Mark_25

On a system you can't easily replace, I'd say yes, 40-50 years is bad, the average home lifespan is longer than that. But I suppose that switching to a different system would be no different than switching from coal to gas maybe.

jw

PEX repipe

As you have old copper in the slab, a repipe from above might be the lea$t painful method in the long run. Would also allow you to zone extensively. Kitec XPA would work well for this app. I like the 5/8" stuff as it is easy to work and has same expanson rate as Cu.

Good luck.

DanHolohan

Levitt

nailed the copper to two-by-fours and then poured the concrete over the whole thing. The wood was in direct contact with the soil. I've got photos of this during the installation. That wood couldn't have lasted long.

Grumpy

I have arranged for a helium spectrograph to be brought in next week. That will isolate the problem. The company said they can locate the leak to within 6 inches of the point of origin. I am looking forward to seeing this in action. The equipment is in the area of $8000 and they guarantee results or I don't pay. Charges aren't all that bad either. $125 an hour with a four hour minimum. I would like to buy that type of equipment if it truly works that well. We have a developement in this area with 312 homes built with copper in the concrete in the early 50's. Lots of them starting to fail. Machine could easily pay for itself if it really works!

Earthfire

Its not just

the cost of the equipment,but the operator skill and the maintinance of the equipment. Operator skill goes up with volumn.