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Radiant Floor Heating/1950's radiant floor leaking


QUESTION: Hi Morgan,
I am fixing some leaks in a 55-year old radiant heat system with steel pipes in the concrete floor here in the Bay Area of California (an Eichler).
There are two types of leaks: one type is near the surface of the concrete which I have typically fixed by removing a section of pipe that includes the leak and then patching across with pcv tubing and stainless clamps. This has worked out so far.
Recently I found a couple of leaks where it appears the original construction played a role in that the damaged pipe was found to be under the slab on the dirt and badly rusted out for a foot or more. I have been able in one case to follow the damaged pipe to ends where the pipe re-enters the slap and seems to be undamaged from there on. Because of the difficulty of exposing the good pipe for a jump connection and extensive concrete removal to access the good ends I have opted to abandon this small area loop by simply plugging at the ends using 7/16" fine thread cap bolts which fit quite snuggly (in fact seem to 'cut' there own treads in the soft steel piping), then hose clamp around the pipe/bolt interface. Would that be a reasonable way to seal off the loop at both ends?
Another leak like that is so long that I sealed the supply end of the loop as above and simply turned off the return end at the manifold, which also seems to work to stop that leak.
Before I fill the holes I have dug would you please comment about the repair I have fashioned?
Should I try to in-case the sub-slap cap-bolt plugs in concrete or simply surround them with dirt and then cover that with concrete to fill the hole?
The system is running well with good pressure retention and a new Grundfos pump (the 25 year old Grundfos quit when these two sub-slaps leaks combined to overwhelm the water supply to the system).
Thanks so much for volunteering. I am also a voluteer in the Chrysler Repair topic at AllExperts.

ANSWER: Hey that was a good year! Like my doctor says, that' not that old. Good thinking on the bolt. I wrap my repair coupling and plugs with rubber or PVC (electrical tape) when I do have to excavate and repair the infrequent in-slab PEX leak. Once wrapped, the concrete should not bother them.

Frankly, I abandon most of the old slab radiant floors from the 40's and 50's since it is very hard to predict the frequency and extent of future failures.

The beauty of radiant floor heating is the efficiency with which it gives off heat. A home can often be made quite comfortable with a third of the floor off. Naturally, in colder climate an outside wall or room with large glass will suffer.

The answer for most of the early leaking radiant slabs, be they copper or steel pipe, is a European style panel radiators or retrofit radiant ceilings.

Best of luck.

---------- FOLLOW-UP ----------

QUESTION: Thanks for your information, Morgan. I will stick with my present system given how well it has worked over the years and its apparent present ability to hold pressure.
But I have one issue to ask you about. As to the several deep holes under the slab where I had to go down to the dirt to affect a repair and the one shallow hole where the adjacent undisturbed surface of the concrete nonetheless 'weeps', because of the duration #I suspect several years# of these leaks both the underlying dirt and concrete in those areas are still apparently saturated.
So my questions are should I wait until all this moisture has evaporated before refilling the holes? Would I want to avoid leaving high humidity so as to not put at risk the remaining steel pipes nearby? Or might that not be important to achieve a dry state under and in the floor?
Either way I plan to put in dry dirt to raise the level in the hole to about 4" below the floor surface, then put in concrete mix in two steps of about 2" each so as to fill these holes.
We can tolerate the open holes for a while so long as we don't twist an ankle.
Your thoughts on the timing would be most appreciated.

PEX repair
PEX repair BadgerBoile  
Unless you have a high water table, there is no such thing as a "wet" area next to a radiant slab of floor. We have many customer that operate their radiant slabs in basements or walk-outs just a couple degrees above the normal summertime temperature, just to keep the perfect dry.

Cover and sleep well my friend.  

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Morgan M. Audetat


Radiant panel heating design, including floors and ceilings, European wall panels and snow melting for residential and light commercial buildings..............................................................-Master of Steam and Hot Water,City of Minneapolis....................................................--- Master Plumber, State of Minnesota...........


30 years..... Charter Board Member - Radiant Panel Association, former manufacturer of condensing boilers, former national distributor of radiant floor products, son and apprentice of mechanical & plumbing contractor. Current mechanical/plumbing contractor specializing in hydronic based, integrated HVAC systems. Radiant floor heating/cooling. Snow Melting. Condensing Boilers. Indirect water heaters. System design, consulting and technical training world-wide. Licensed contractor, designer, installer and consultant.

B.S. University WI 1981 CONTINUING EDUCATION: Viessmann Condensing boiler and Solar water heating certification 2010, N.D.S.U. Lead Worker RRP certification 2010, Knight condensing boiler certification 2009, Wrightsoft Manual J CAD certification 2009, RPA Designer & Installer Certification 2008, Nate Hydronic/Forced Air Certification 2008, Uponor/Wirsbo advanced design school certification 2007, Buderus Wall-hung certification 2007, Power Limited License (low voltage controls) 40 CE credits 2005, Basic Hydronic Certification IPEX & Northern Alberta Institute of Technology 1998, Charter Board Member - Radiant Panel Association 1994, Residential Off-Electric to Hydronic Conversion Heating School Canadian Hydronics Council 1994, B&G Little Red School House 1993, Rood Utilities (now Auburn Technical Institute) Oil Burner School 1993 ,Tekmar Controls residential and commercial 1993, Division Manager and Advanced Hydronic Seminar Instructor for the first Exclusively Hydronic Radiant Floor Distributor in the USA 1990, Hydronic Radiant Heating Association Workshop participant with Richard c. Bourne, PE spring 1988, Master Plumbing, Hydronic, Solar Course Red Rocks Community College 1987.

Awards and Honors
2009 System Showcase Award - Radiant Panel Association

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