I have radiant heat in GypCrete under slate flooring. It has leaked quite a bit of water to the point we had to shut it off. What does that mean? The house is only 4 years old.  Larry.

Some thin-set manufacturers still hold to the belief that gypsum has inherently low tensile strength and possesses weak surface layers that are prone to dusting. These manufacturers do not recommend gypsum as an underlayment for ceramic tile - especially in wet areas. Most recognize the biggest problems are posed by weakening of the gypsum by water or moisture exposure and chemical reactions between mortar and gypsum that form bond-breaking ettringite compounds.

Finally, someone with the same knowledge of Gypcrete that I'm familiar with! Gypcrete IS PROBLEMATIC to say the least

What are the best types of carpets to prevent falling and also to install in a home for a wheelchair or scooter user?
: Working on a new construction side, has concrete slab, the customer thinks they also want the slab to be coated in gypcrete...any hazards I should be aware?  thanks
As most have already stated gypcrete is definitely to be avoided especially where wheelchairs are involved. It does not have the compressive strength and will wear underneath any soft surface product installed over it. This will produce delamination in a carpet products.

Your "hunch" should be right... Though the material is well known and is a derived of epoxy.. It is recommended here (since my own work alas that served as a test on 10 000 sq m) to have that epoxy preparation before applying linoleum on concrete floorings, specially if they are "new" (not old in age and moisture evaporation) otherwise you will have sort of mole paths under the lino slightly swelling on invisible cracks...
In the case of gypcrete (does that thing still exist?) it seems that this one is getting to powder in some parts (is it a concrete floor or a wooden one?). If those parts are small in area you can give try with a syringe... But the best would be to cut properly the lino in those areas in a pattern fashion and to replace it by another in different shape or color after having treated the gypcrete....
But that's not really resolving anything, the best, being to get that gypcrete stuff "out" definitely... It can be a nice product when very well and thoroughly applied ... but usually the hygrometry variation tends to desiccate it to powder (too much heating) or it can break in granulates after some hard encounters with furniture....If applied to soon on "fresh" concrete it doesn't stick properly, etc...

Problem with Radiant Heating leak, Gypcrete and wet bubbleinsulation=BIG WET PROBLEM
  I finished building a 3500 sq ft home with contiguous floors on a concrete slab 5 years ago. I had installed a Munchkin radiant heat system for the floors, with a separate system for the domestic hot water.
  Big Problem. The run was so long from the boiler at the front of the house to the back, my contractor used copper pipe to supply 6 valves in the back of the home.   The copper pipe cracked, and saturated the entire 1/4" heat insulation blanket, so water soaked the gypcrete. On top of the gypcrete I used a Ultraset Hydroment membrane for the wood and slate tile floors. The wood floors nearest the leak are loose, the slate tiles is still tight, but wet.
  We used a FLIR E-45 and it showed the water as black next to the glowing red radiant pipes THROUGHOUT THE HOUSE.  Since the water migrated UNDER the insulation through the holes where the radiant heat piping was shot down I have 3000 feet of wet gypcrete.
  With 1.5 million dollars of finish improvements sitting on top of these unstable floors, I do not know what to do.
  My contractor says that it is not his fault, and two water restoration companies said that I may have to remove everything down to the concrete subfloor.
  The gypsum walls are wet up about 4' where the concentration of water was most active, the rest of the house has wet floors.   Some say that it will dry with no mold, others say that it will never dry.
  The gypsum walls are growing mold in a few locations, I have had reading taken and black mold is present.
  I have to figure out what to do now - -

Hi, Do you have experience with trouble shooting problems with radiant floor heating or be able to refer us to a website that does? We have a system, 4 years old, it started gurgling that we could hear at the manifolds. Then we noticed the pressure was down in the system. We add more water and pressure drops again. What is the best way to determine if we have a water leak in the tubing (in gypcrete) or could it be the pressure tank? Any ideas for us? No signs of water leaks.     Thanks, Theresa