Page 1 of 3 123 LastLast
Results 1 to 15 of 32

Thread: Radiant Floor Heating

  1. #1
    Join Date
    Jan 2011
    Location
    Northern UT
    Posts
    745

    Radiant Floor Heating

    I have been running my radiant floor heating for about 180 months. Works great other than one thing. I keep losing pressure in the closed loop system. I have four loops, with a single zone and pump. Running it off an on-demand water heater and normally set it at 20 psi.

    Every couple of weeks I see that the pressure has dropped to around 3-5 psi. I hook up my drill to a small water pump and bring it back up to 20 psi. I cannot find any leaks, no water at all on the floor or spots where the pipe is leaking. This is getting old frankly and I simply don't have a clue at this point. I checked the expansion tank and it is at 12 psi.

    The top of the loop of my system is about 6' off the ground.

    If anyone has experience, thoughts or suggestions I would appreciate them.

    Thanks in advance.

  2. #2
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    56,206
    Do you perhaps have a slow leak somewhere in the slab?
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
    Join Date
    Feb 2010
    Location
    Mt Pleasant SC
    Posts
    665
    Check the TPR valve on the top or side of the water heater. If the discharge pipe is piped to a place where it’s not readily visible you would not know it was discharging other than the pressure drop. There might be an expansion valve too. When those fail they damage the TPR valve.

  4. #4
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
    Posts
    5,588
    I will put a clean paper towel under a suspected drip. Even hold it on with a rubber band. Come back in a few days and see if there is any water staining on the paper. I have read of people dusting flour on their engine to find an oil leak.
    Bil lD

  5. #5
    Join Date
    Nov 2009
    Location
    Alaska
    Posts
    345
    Is this a new problem? In my experience, radiant floor heat systems need a very thorough air removal after it is first commissioned, and you also need a good air vent (Spiral Vent, preferably). If it does have a vent, then you should check it out and make sure it still functions correctly.

    If you do have a leak in one of the loops (in the slab), and it's not so bad to create a wet area in/on the slab, a good way to find it is to use an thermal camera. Many electrical shops carry them nowadays.

    Additionally, some water in a closed loop system will be lost over time and needs to be made up. That's why you plumb in a fresh water feed. Does your system have this?

  6. #6

    I have in my lap...

    Two books that will delight and inform you. Dan Holohan’s “Pumping Away” & “Primary-Secondary Pumping Made Easy”. Dan writes in a way that the lay-man can understand, which is not an easy thing to do. Depending upon how your system is piped it may drawing air due to circulator and expansion tank location. What tankless are you using? Oh, and Bill, This thread without pictures..., well, you know the rest.

  7. #7
    Join Date
    Jan 2011
    Location
    Northern UT
    Posts
    745
    Answers to a few questions or points.

    1. Pretty much this has been going on since I first started using the system about 18 months ago, but it seems like it is worse this winter than last.

    2. I have a vent on the system designed to bleed out air. I have run the system with it open as the company that designed the system said to, and with it closed. Doesn't seem to make any difference.

    3. I do not have a supply line as I did not run any plumbing to the building.

    4. There are no leaks or signs of leaks at all. I use the paper towel trick any time I do plumbing work. I did it here too and after a couple of weeks, no sign of leaks. When I first turned the system on, I did have a couple of leaks, one in a sweat weld and one in a threaded connector. I solved both and have not been able to find any leaks since. No wet spots on the concrete at all.

    5. I have a pressure relief valve on the supply side of the tankless heater, and one on the system as well. Neither have any water leaking out at all. At least not enough to create a droplet of water. Neither have tubes on them, so both are easily visible.

    I have never tried to measure how much water I putting into the system each time, but my guess is it is very small amount. I tried changing the pressure in the pressure tank and that didn't seem to have any real effect either.

    One odd thing I noticed is that since the beginning, the highest pressure I could get was 20 lbs using the drill pump. The gauge would hit 20 psi and peg there. The last time I added water, about three days ago, it suddenly went to about 35 psi. No idea why.

  8. #8
    How are you purging the air? The best way is to hook a hose up to it and run each zone individually at the buildings water supply pressure. Running the water at a higher pressure and velocity will tend to pick up the air trapped in the system. Do you have purge valves on each leg of each return? Are you running the system with the air vent open? If so, that can be the source of your air. Have you checked back with the folks who sold you the system? Any suggestions from them. I am assuming you are running a Takagi.

  9. #9
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    1,286
    If you can't find the leak you could always plumb in a pressure tank. You could either run a garden hose to fill/ pressurize it or mount it to a dolly and roll it to your water source. I suspect if it takes weeks to bleed off 20 psi then it would take months depending on what size pressure tank you use. Just make sure to plumb in a pressure regulator.

  10. #10
    Join Date
    Dec 2008
    Location
    versteeghbv@gmail.com
    Posts
    17

    Pressure Leak?

    If you can post picture of manifold and piping it would help a lot. Do you have expansion tank? How many feet of tubing and number of loops in system? When you filled the system did you use a purge pump? Getting all the micro bubble out of the system can take a long time just using the system pump.

  11. #11
    Join Date
    Mar 2003
    Location
    Central PA
    Posts
    82
    I also have a radiant floor in my shop (14 years old). I was thinking you might have air pockets trapped but this is unlikely after 18 months of operation. How long did you pressure test the system with air, and at what pressure, prior to pouring the slab? If you don't have a leak anywhere above the slab then it is in the slab.

  12. #12
    Join Date
    Nov 2009
    Location
    Alaska
    Posts
    345
    Quote Originally Posted by Mark Blatter View Post
    Answers to a few questions or points.

    1. Pretty much this has been going on since I first started using the system about 18 months ago, but it seems like it is worse this winter than last. My initial thought is inadequate air removal after it was first put into service.

    2. I have a vent on the system designed to bleed out air. I have run the system with it open as the company that designed the system said to, and with it closed. Doesn't seem to make any difference. Oh it will. Leave it aligned, always. I use SpriroTherm in my home, as other systems I've installed. https://www.spirotherm.com/products/air-elimination/animation

    3. I do not have a supply line as I did not run any plumbing to the building. I suggest you consider installing a stand alone system for adding make up water. You do not need a visible leak to lose water.

    4. There are no leaks or signs of leaks at all. I use the paper towel trick any time I do plumbing work. I did it here too and after a couple of weeks, no sign of leaks. When I first turned the system on, I did have a couple of leaks, one in a sweat weld and one in a threaded connector. I solved both and have not been able to find any leaks since. No wet spots on the concrete at all. Again, it is normal to lose water in a closed system, even though you do not see a leak.

    5. I have a pressure relief valve on the supply side of the tankless heater, and one on the system as well. Neither have any water leaking out at all. At least not enough to create a droplet of water. Neither have tubes on them, so both are easily visible.

    I have never tried to measure how much water I putting into the system each time, but my guess is it is very small amount. I tried changing the pressure in the pressure tank and that didn't seem to have any real effect either.

    One odd thing I noticed is that since the beginning, the highest pressure I could get was 20 lbs using the drill pump. The gauge would hit 20 psi and peg there. The last time I added water, about three days ago, it suddenly went to about 35 psi. No idea why. Air compresses, water does not.
    Jack Fredrick's rec is good. When I plumb a system, every loop in every zone will get isolation valves, and a hose bib to hook up a garden hose and purge the loop with a steady stream of water. Once purged, I move on to the next loop in that zone. Once all loops are purged in the zone, then it's to the next loop in the next zone. After the entire system is purged of air, you will still hear air hissing out of the Spiral Vent for day or two.

  13. #13
    Join Date
    Dec 2008
    Location
    WV
    Posts
    4,375
    Do you have an expansion tank in the system? A closed loop low pressure/high temperature system (which yours isnt) would have an expansion tank because when water is heated it expands. In an closed system as you describe without an expansion tank your pressure would fluctuate high when the water is hot, low when its cooler. Even in low pressure closed loop systems (with perhaps a 15psi pressure reducer feeding the system) we would always leave the feed open. With the pex loop it will allow for a bit of expansion contraction with a change in water temperature (pex is flexible). Any slug of air would act as a cushion and show fluctuation in pressure with temp rise/fall but if there is no leak it would remain constant.

    You may be seeing increased/decreased pressure simply based on how hard the system is running, the average system temp, ambient, etc.. If it never drops below a given pressure I would say there is no leak. If you had a leak the system would typically bleed off to nothing eventually.
    Last edited by Mark Bolton; 01-18-2021 at 1:28 PM.
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  14. #14
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    1,286
    Since it was designed by a company I have to believe it has an expansion tank. But they don't hold much water, maybe 2 gallons or so with some less than 1 gallon. That's not going to provide much makeup if you have a very slow leak. If you're lucky you could have valves on each loop and shut one off at a time to see if the problem resolves itself. If so then you know you have a hole in one loop and most likely in a place you can't get to. At least then you can decide if 3 loops will be enough (maybe for all but the coldest of days).

  15. #15
    Join Date
    Dec 2008
    Location
    WV
    Posts
    4,375
    If it doesn't leak down to pretty much nothing over time there is likely no leak. In a low pressure system like that there is really no need for pressure anyway. The reason for pressure is no different than in your auto radiator, to raise the boiling point of water. In a radiant system with a low temp water heater feeding it pressure is irrelevant.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •