Should I do an acid clean on a 70 year old CI radiator system?

R2.0

When I commissioned the new boiler in my system I purged it per the WM manual - close all the radiator valves except the farthest, run water through, open the next closest, etc. 3 issues:
- My radiator valves, while all operable, aren't shut off valves. They only turn 180deg.
- I could never get the water to run clear. With each rad it would start out black, and it would never really clear up.
- 20+gpg water hardness.

When researching here I've seen debates on phosphoric acid cleaning, mostly on steam systems. Any thoughts?

SWEI

I would purge the system (zone by zone, or however you can break it up) using line pressure water until it ran clean, then install a magnetic dirt separator. Fill with water and a cleaner (e.g. Rhomar Hydro-Solv) and run for a couple of days, then refill using a lower hardness water (bottled if necessary) along with an inhibitor. Drain the separator regularly until you stop seeing crud.

R2.0

Those were in the plans already - regardless of how much I flush there's no way it will get all that magnetite out.

Does softened water meet the bill?

Captain Who

I know this isn't much help to you, but what's a "CI" radiator?

I just flushed a single radiator and associated dry/wet return in my steam system and I never got perfectly clear water either, but it did get a lot cleaner. Most of the return piping was brass or copper, but the stuff near the radiator was iron. I was wondering if I would have to take it to the next step of using some sort of acid (I have some citric acid powder already on hand), but the problem of the spitting radiator vent was solved so it was unnecessary to go any further. I flushed them separately but I guess (you don't say) that you are flushing through the top of the radiator down through the return?

R2.0

Captain Who said:

I know this isn't much help to you, but what's a "CI" radiator?

Cast Iron

Captain Who

Thanks......Cast Iron....shoulda figured that one out. Sorry but one more question......is this a hot water (HW) or steam system (SS)? If it is steam I wonder how much minerals would get entrained in the steam. Theoretically it would be like distillation where all that remains in the boiler pretty much.

R2.0

HW for me.

SWEI

Salt-based softening trades calcium and magnesium for either sodium or (less commonly) potassium. It also adds chlorides. I'd call Rhomar and ask for an opinion before I did that.

If it's a small system, I'd fill it with at least 80% RO water. Hardness in the 3-4 GPG range is about optimal.

R2.0

I really wouldn't have a problem using bottled distilled - but for the fact that my system volume is something like 20 gallons, and I'm not sure how I would fill it.

SWEI

Too small to make renting a DI tank economical.

Take a clean plastic barrel down to the local bottled water joint and have it filled (or find a friend with an RO system and be patient.)

R2.0

My town has it's own water plant, where they pull from wells (hence the hardness). I'll give them a call and see if there's an RO/DI setup there. Otherwise I can go to a friend's place and fill up on WSSC's finest from the Potomac.

SWEI

Good luck with the project.

If you have a chance, do us a favor and report back once the work is complete. It helps both other people with problems (this site gets a lot of search hits) and those of us who try and solve them to see how it all works out.

R2.0

Oh, I'll be back - my list of potential system upgrades is as long as my arm.