Something I keep reading

Bomba

I keep seeing in posts on The Wall the mentioning of a leaking steam valve (maybe a radiator supply valve) causing early decay of the steam boiler itself; though, I don’t understand the correlation. To me it’s like saying if the hot water on my faucet drips then my hot water heater is going to rust faster. 

What am I missing ?

ratio

With the steam system, all the water that leaks out must be replaced. The replacement water contains dissolved oxygen & minerals, both of which are detrimental to the boiler.

Bomba

Oh. So it’s not the leak, it’s the replacing of water. 

Makes sense. 

Thanks 

Bomba

I wonder if there’s a way to treat the water before we put it into our boilers so they don’t prematurely rot. 

Jamie Hall

Yes.... there is, and it's used on big power boilers. A combination -- carefully monitored in laboratories on-site (or on board, for ships!) -- of oxygen scavengers, pH buffers, and protective film forming materials.

All of which are toxic -- some extremely so -- and hard to handle.

And they still rust out, but perhaps not as fast (one hopes). At upwards of 600 psi on many of these things, one wants to be careful!

ratio

Or try what Mr. Holohan suggests here & run the makeup water through a water heater first.

Bomba

Yeah my boiler fill comes from my water heater. I thought it was to prevent someone putting cold water into a hot boiler. Maybe it does both. 

nicholas bonham-carter

A system in good condition will not need much makeup water in a heating season, and so the potential for rust is very low; but if the system is not maintained, and develops steam leaks, or water leaks, more fresh water is brought in and wakes up the rust, (it never sleeps anyway).—NBC

SteamingatMohawk

For the experts here (and I am certainly not one). how does the makeup water oxygen and minerals in a non-leaking system compare chemically to the effect of air being expelled then drawn back in on every heating cycle of the system?

Unless the makeup water is truly horrible, my uneducated guess is the constant flow of air has more corrosive effect.

What say "you all"?

ethicalpaul

Apparently, the fresh water has way more dissolved oxygen in it than your condensate water. This then gets forced out as you heat the water and is like an oxygen injection into your system. And yes the fresh air that gets drawn into the system brings oxygen, but my understanding is that it doesn't dissolve into the system water nearly to the level that oxygen is in the fresh makeup water.

Especially city water where I have read that municipalities actually oxygenate the water in order to improve the taste!

As for minerals, that's pretty straightforward. The less water you have to add to replace lost steam or condensate (like from a buried return), the less minerals will be introduced.

Jamie Hall

One has to have pretty vigorous mixing to get much air to dissolve in the water -- as well as a good bit of surface area. Neither, really, are present in a steam boiler, and out in the steam pipes what little water is (or should be!) left has almost zero conductivity, so very little corrosion. But some -- as we all know from leaking wet returns!

jhrost

Reminds me of a neighbor who fed hot water into his boiler from the water heater. The boiler was a roundish asbestos covered old thing that I think some of the people on this site call a 'snowman' - it has to date from at least the 1940's and probably earlier and it is still going. I'm not sure how efficient it is or how well it heats though.

Zipper13

I suspect as well that many of the dissolved chemicals and minerals stay dissolved in the liquid water in the boiler and are not boiled into the steam. If that is the case, then as steam is lost and water volume decreases via by leaks in dry lines the mineral concentration in the boiler increases since the original amount of chemicals are still there but in a now smaller volume of water. So the water escapes, but the other minerals and chemicals do not. Then as one adds makeup water they introduce more chemicals. repeat over the season and I would expect that the concentration of water treatment chemicals or whatever might be in one's well water supply is absurdly higher than the concentration fresh out of the tap

ratio

@Zipper13, exactly so.