Installing a hot water heating system without a plumbed in water supply

Bart32

I am planning to install a radiant floor heat system in my shop which does not have a direct water supply. I would like to use a small gas wall mounted boiler and am wondering how to handle the feed water supply. I cannot easily bring a frost proof water line from my house so I am thinking that a water tank of some type could be used to supply water to the system. Since it is a closed system I presume it shouldn't need much water and perhaps all I need to do is top it off occasionally. I can run a temporary hose to fill the system as needed or use a small pump to inject water from a bucket.

It seems to me that if I used a large enough pressure tank it could maintain the necessary pressure even with a loss of several gallons of water.

SWEI

We rarely install automatic water feeders (at least on a permanent basis.) If your system is tight, it should not need water more than perhaps a tiny bit every year or two.

Oversizing the expansion tank will not cost much and it does add a bit of a safety margin.

hot_rod

In a shop, you may consider using glycol also. You could also use a glycol fill tank, like Axiom and others. They get used with water or glycol.

SWEI

To be fair, Axiom really does make great stuff.

In this particular case, an oversized expansion tank can probably cover it.

hot_rod

If the potential loss you want to cover is several gallons, consider a PIG.

A separate expansion tank, filled to 80 psi and attached to a pressured reducing fill valve. With a small #30 tank you can get around 3 gallons, or a #60 about double that.

Expansion tank, Webstone purge port valve, boiler fill valve, wash machine hose and adapters

Bart32

Thank you all for your very helpful comments and suggestions. I am not expecting any fluid loss as this is a new floor installation and shouldn't have any leaks. I will be using antifreeze in the system since it won't be heated at all times. I will probably just use an over-sized expansion tank and, if it loses a little pressure, I'll top it off with a hose from the house.

hot_rod

Yeah, if the system is tight, no worry. Within a few weeks of operation all air should purge itself out. Use a micro bubble type air purger, glycol is tough to scrub micro bubbles from, it gives up air very slowly. Temperature and time to get them 100% air free, you may need to add some fluid for a few weeks as it operates.

The Germans call that over size, over pressurization expansion tank a "safety seal"

Remember the pressure gauge will drop when the system is cold, sometimes this gets mistaken for a leak. We get that call on solar thermal, they fill it on a warm day, next morning the pressure has dropped and they panic.