Reverse osmosis water for in-slab hydronic heating?

OhioBarnBuild

Hi all,

I'm almost ready to add water to my new in-slab hydronic system and wanted to ask about using reverse osmosis (RO) water. I see the question has been asked before but it looks like the last time was a few years ago and I’m wondering if there’s anything new under the sun. My system design also seems a bit different than those of the people who asked the question before.

I’m running a Laars FT series combi boiler, about 5,000 ft of ½” PEX tubing with oxygen barrier, stainless manifolds, a brass Taco air separator, stainless Taco circulator pump, Extrol expansion tank, and copper tubing to connect it all. I was originally planning to add glycol for freeze protection but reading all the feedback here changed my mind so I plan to just run straight water. The site is on a well and that water is very hard so I won’t be using it for heating.

We have a large RO system at work. We add a little chlorine to keep stuff from growing in the water while it’s in a holding tank and keep that at 0.8 ppm. The pH after the chlorine is added is 6.53. The system filters more water than we need so I took in a clean, plastic 55-gallon drum and filled it up. Per the boiler manufacturer’s recommendation, I plan to add a corrosion inhibitor (Adey, Fernox, Noble, PurePro, Rhomar, or Sentinel, per the manual).

Given all that, is this RO water with a corrosion inhibitor the way to go or am I potentially creating other problems?

Jamie Hall

That should work, with the corrosion inhibitor. It's not really a popular option because of the cost and most systems don't really need it, but if you can get the stuff cheap it is a little better.

kcopp

here.
This will do the job much simpler and faster.

https://axiomind.com/axiom_products_cat/h2o-demineralizer/

hot_rod

If you have the RO water, that is great for filling. Ph will buffer up in a few days by itself. I agree adding the conditioner, it will buffer the ph up right way. Plus film providers, plus oxygen scavengers Get a test kit with the conditioner and check the fluid every year or two.