Flushing Cast Iron Radiators

lkosy1

I just got a new mid-efficiency system from LAARS that works nicely in my 3 story home. I have had an old plumber that does everything else in my home. The new plumber for the LAARS system says that my radiators are full of sludge after 100 years of use and should be flushed using a chemical product. My old plumber says that he never hear of doing that - that the system is meant to be maintained as a closed system. Who is right? (BTW - the old plumber would be getting the job. I like hime better. So it is strange he is talking himself out of a job!) Thanks

SWEI

How is your water quality there? Was the old system using a lot of makeup water?

Drain a bit of water from a low point (boiler drain) into a clear glass and hold it against a white sheet of paper. How does it look?

Water treatment might still be a good idea.

lkosy1

The system was working very well- we never had to add water. I shall look for the boiler drain and find out. God idea.
I know when the new boiler was swapped in last year, the dirty water was endless.

lkosy1

I drained a glass of water from the boiler - it is not quite crystal clear; the water looks ever so slightly gray - very slight. Of course, since it is May, the boiler has not been on for quite a while, if that makes a difference.
Thanks

SWEI

That sounds like it could be hematite. Put a strong magnet next to the glass and see what happens.

kcopp

Depending on the boiler you have and how tight the water passages are I would seriously consider adding a good cleaner, flush out and then an inhibitor. A belt and suspenders approach would be to add a Magnet type filter on the boiler return.
fernox and Caleffi both make them.

http://www.fernox.us/equipment/filters/tf1+total+filter

lkosy1

I spoke with my installer and he says that he put a "dirt separator with magnet" filter on it already, which is why there was no sludge when I took water from the boiler.
He is advocating that I drain the whole house and flush it to increase the efficiency of the system, and theoretically with the filter, I should not have to flush it ever again.
Can anybody tell me why my old school plumber says that the accumulated stuff (sludge, whatever it is) is not a problem, while the high-tech guy says it is? And what is that sludge, anyway? How can it accumulate in a closed system like that?
Thanks

hot_rod

A hydronic cleaner would not hurt. Problem with flushing old radiators is getting enough flow to move the sludge out. You want 6-8 God velocity to really flush heavy sludge out

It takes a good sized purge pimp, or pump

hot_rod

Sorry about tried to post fps

High velocity in large pipes and vessels takes lots of gpm. Something like a pool pump