Boiler periodic flush needed?

[Rman]

I have a 20 year cast iron one pipe boiler with cast iron radiator’s
Is it necessary to periodically draw down the boiler water and fill up as marked on the sight glass. The water is very rusty brown. But next week it’s rusty brown again. I’ve gotten both ways from different plumbers. The boiling water is dangerous to get from pail to slop sink. No floor drain. Thanks

 

[SWong]

I have a 20 year cast iron one pipe boiler with cast iron radiator’s
Is it necessary to periodically draw down the boiler water and fill up as marked on the sight glass. The water is very rusty brown. But next week it’s rusty brown again. I’ve gotten both ways from different plumbers. The boiling water is dangerous to get from pail to slop sink. No floor drain. Thanks

Very good question RMAN and I also would like to know. Me, I've always flushed and backflushed after each and every heating season simply because all that rust and trash eventually makes it difficult to read the amount of water via the glass sightgage. All that rust and dirt impedes the making of steam I suspect so why not drain and flush after each season? Besides, all that dirt and rust simply cannot be good for efficiency along with the fact it tends to coat the low water shutoff probe. I've got a Peerless IN6 steam boiler going on 12 years of reliable use having only been down for a replaced standing pilot light thermocouple which I replaced myself.

 

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[Fitter30]

Steam boilers need to be blown down every week or two to keep total dissolved solids down with if they get to high the boiler will start priming. Thats where the water bounces in the site glass and over fills the boiler. Why don't you wait till the water cools off before empty your bucket.

 

[Reach4]

Steam boilers need to be blown down every week or two to keep total dissolved solids down with if they get to high the boiler will start priming. Thats where the water bounces in the site glass and over fills the boiler. Why don't you wait till the water cools off before empty your bucket.

Seriously?

 

[Jadnashua]

A steam boiler is quite different than a closed hydronic system. Flushing a closed system just invites additional rust. The refill water will contain some dissolved gasses, which includes some oxygen. In a closed system, it shouldn't lose any water, over a fairly short time, all of the oxygen gets used up making rust, and it becomes quite stable. Only if you have a leak and need to keep adding water will it continue to rust those susceptible components. Constantly adding water that leaks out will shorten the life of many components.

 

[Plumber69]

I have a 20 year cast iron one pipe boiler with cast iron radiator’s
Is it necessary to periodically draw down the boiler water and fill up as marked on the sight glass. The water is very rusty brown. But next week it’s rusty brown again. I’ve gotten both ways from different plumbers. The boiling water is dangerous to get from pail to slop sink. No floor drain. Thanks

You mean expansion tank? If so just get a diaphragm one

 

[Jadnashua]

Older boilers often had an expansion tank, essentially open to air. The water would absorb that air over time, and eventually fill with water, thus, no expansion possible, or severely diminished. On those, you do need to drain them periodically. But, constantly adding air to your hydronic system will constantly be rusting things from the inside out. A diaphragm based expansion tank keeps the air and water separated, and, generally requires no periodic maintenance, but will need to be replaced more often than the older type.

 

[Dana]

You mean expansion tank? If so just get a diaphragm one

Steam boilers don't have or need an expansion tank. The system is normally filled with either air or water vapor, which are highly compressible, and a typical residential system would/should never exceed 0.5 psi.