I installed Pex tubing in concrete in 2 areas, both garage floors. I have been told 2 things…. one is that it will require a boiler, two, that a hot water tank will do the job. Cost is a huge factor here when compared. I am willing to try the hot water tank as it is a fraction of the cost and can use it on another property if not successful. Any thoughts on this would be appreciated.
Water – Can i use a water heater as the source for the in floor Pex tubing system
heatingwater-heater
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Dry all the suspect areas well. Wrap a paper towel around each inlet/outlet. Turn on your hot water draw and start checking the paper towels. the first one to get wet is where your problem is. Then it my just be a matter of tightening a connection or removing and replacing a soldered fitting.
I suspect you have a set-up like this?
You are concerned that when the water gets pumped back into the "water heater" it could possibly pollute your main water line?
The only thing I could suggest is putting a check valve on the "cold" water supply so that it can only supply fresh water. That is helpful if the pumps output pressure is higher than your supply pressure (This could happen on someday with low supply pressure or if you do not have main water pressure regulator)
In this situation the return is a dedicated port on the "water heater/boiler" and there should already be a check valve/pressure regulator/non return valve just before the water heater. So the rest of the house will run just on the cold water supply and never get any recirculation contamination.
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Best Answer
It's all about heat load.
A very well insulated building may have a heat load so low that most boilers would be operating very inefficently to meet the load - sitting idle most of the time, even on "design days" when the heat load is at the greatest due to the outside temperature being the lowest temperature designed for (thus, "design day.")
As a practical example, I have a radiant floor system installed in a building with a design-day load of 30-36,000 BTU/hr. A typical "small" boiler is 100,000 BTU/hr, so it would be in standby 2/3 of the time even on that coldest day (which is typically for no more than a week, and not every year.) A water heater can be more closely matched to the load, simply because they are available in smaller sizes.
As for tank .vs. no tank, it's largely irrelevant - there are inefficient and efficient versions of both (and much of the hype for tankless heaters being "more efficient" due to no standby losses falls down in houses where hot water is actually used, at modern insulation levels which lower standby losses; especially considering greater complexity and maintenance expense that is often associated with tankless.) A common example (and commonly used for radiant heat) of an efficient tank type is the polaris, at something like 95% efficient and a condensing design.
If you have a larger heat load, an efficient condensing boiler might be a better choice - that has to to with the whole building construction, not the heat delivery method.