Boiler water maintenance

neals

Thanks to this forum my ancient radiators have been behaving OK with my new boiler for more than a year.

I've read conflicting advice on managing the boiler water, though. On one hand every bit of new water added has dissolved oxygen that will damage the system, especially the boiler. On the other hand, gunk in the water will clog vents and reduce overall efficiency. So what's the right balance?  Should I be draining coffee-ground-laden water out of the lower boiler valve weekly, like my mother-in-law used to do with the old boiler?

Jamie Hall

No. If you have a float type water LWCO, that should be blown down (valve at the bottom of the float chamber) two to four times a month. Otherwise, the boiler does not need to be drained except, perhaps, once a year.

KC_Jones

neals said:

Thanks to this forum my ancient radiators have been behaving OK with my new boiler for more than a year.

I've read conflicting advice on managing the boiler water, though. On one hand every bit of new water added has dissolved oxygen that will damage the system, especially the boiler. On the other hand, gunk in the water will clog vents and reduce overall efficiency. So what's the right balance?  Should I be draining coffee-ground-laden water out of the lower boiler valve weekly, like my mother-in-law used to do with the old boiler?

You should only be getting steam at the vents, it is the most pure thing in the system. If you are getting gunk at the vents, that's another problem unrelated to water treatment. The water treatment stays in the boiler.

I treat the water and drain nothing. As a "test" of the water treatment. I didn't touch the water side of my boiler for 3 years, didn't open a valve, didn't blow anything down, just let it run and add fresh water as needed. After 3 years the drains all flowed freely, I had very little gunk in the boiler. Basically open a valve and get a quart of brown then clear, from every valve. The wet return is always clear because it's piped in copper.

I'm a huge advocate for treating the water, to me it makes the most sense. The boiler cost me a pretty penny and a bunch of labor, I want it to last as long as possible.

SteamingatMohawk

Coffee ground laden water? If the material has particles that large, it seems odd. I have an almost 100 year old system with a 20 year old boiler and used to drain a few ounces every week to minimize the sludge. I stopped doing that to reduce consumption based on comments on HH .

I tend to believe any dissolved oxygen would get purged when the new water boils. I am not enough of a chemist to know the solubility of oxygen at 212F.

cross_skier

I keep pH around 10, do a blow down once a year, and have insulated mains and installed 1-1/4" galvanized returns to help reduce carbonic acid.  I pipe in my new water into a return about 10' from my boiler. 

SteamingatMohawk

The chart is from Engineering Toolbox. Basically when oxygenated water is boiled, the solubility goes to 0.

Oxygen saturated water at room temperature (20C or 68F) contains around 8 milligrams per liter. If makeup water is added infrequently, that isn't much. Mine adds 2 gallons every 2 weeks.

I believe the air sucked back into the system every heating cycle when it cools down has a far greater effect.

neals

So it's not the oxygen, maybe it's the dissolved chlorates or other impurities?

I believe my LWCO is electronic somehow. What is a blow down?  Is it opening the bottom valve and letting hot water out?  If so, how much?  I haven't touched it since Christmas Day 2020, when I did a skim after the boiler was serviced by a great NYC area pro I found on the forums here. 

EBEBRATT-Ed

If the low water cutoff is a probe type the boiler should be drained and flushed yearly clean the probe and the pigtail under the pressure control