Draining a boiler at the end of each heating season

SteamworkS

I see that this has been a topic in the past, but wanted to bring it back up since I see two different schools of thought on draining the boiler completely at the end of each heating season.

It seems that from what I read or hear most people do not suggest draining a boiler completely at the end of the heating season. Rather many recommend draining only what's needed to clean out the bottom layer of water in the boiler and what is needed for proper maintenance of the LWCO. Too much fresh oxygenated water leads to premature rust in the boiler and pipes.

However, recently Dan sent out a suggestion based on literature he had read from one of the Dead Men. Please correct me if I'm wrong, but I think it suggests that perhaps leaving water in the boiler leads to more rusting in the pipes because oxygen enters the condensation lining these pipes. The condensation comes from a water filled boiler quietly sitting idle all summer. Since the boiler isn't firing periodically, the distilled water doesn't remain distilled but becomes oxygenated over time - at least the thin layer of water that contacts the pipes. Draining the boiler completely leads to evaporation of water in both the pipes and the boiler and therefore lessens the amount of rust that occurs.

Thoughts?

For me I suppose it doesn't matter since even if I did drain my boiler at the end of each heating season, I can't drain my wet returns and so will always have a pool of water in the system.

Fred

An empty boiler only provides more surface area exposed to oxygen and moisture. You simply can not dry a boiler out and eliminate the moisture withous some kind of absorbtion chemistry. The system is open to the atmosphere, via, vents so there will always be some level of moisture/oxygen. My pipes are 114 years old and are still as solid as a rock. Boiler remains filled throughout the summer. Besides, if the pipes were to be the sacrificial component of the system, that's a lot easier and less costly that a boiler replacement.

ChrisJ

Now that Fred has set him self up for some leaky pipes this winter...

I believe in using water treatment all season and then draining, rinsing and refilling and then adding fresh water treatment in followed by immediately boiling the water.

Another option, which may the best, is to follow Rhomar's instructions of using their Boilerpro 903 water treatment which has a good oxygen scavenger and filling the boiler right up into the piping for the summer.

Fred

ChrisJ said:

Now that Fred has set him self up for some leaky pipes this winter...

I believe in using water treatment all season and then draining, rinsing and refilling and then adding fresh water treatment in followed by immediately boiling the water.

Another option, which may the best, is to follow Rhomar's instructions of using their Boilerpro 903 water treatment which has a good oxygen scavenger and filling the boiler right up into the piping for the summer.

I know! I debated if I should even utter those words

SteamworkS

Thanks guys. Makes sense. I'll keep it full and will maybe look into the Boilerpro 903 water treatment.

Abracadabra

I always fill boilers up with the water level into the risers and before the header. This provides a lower surface area for oxygenation of the boiler water. I run the boiler to the point where steam begins to fill the main and then shut if off until start of the next season.

KC_Jones

As an experiment this year I did the same, filled the boiler into the risers then ran the boiler until steaming. Once the whole thing cooled I actually closed my king valves and the valve in the Hartford loop. My thought was this essentially eliminates any possibility of fresh air getting to the boiler. I have no idea if it was a good or bad idea, it is simply an experiment.

makinsteam

How do you guys know when the water level is into the risers? I discussed this with my contractor and he suggested timing how quickly the boiler fills and then estimating when it will reach the risers. I'm just curious if there is any trick or if this is the method. I'm considering cracking the unions on the risers and filling very slowly and stopping once I get a drip, but maybe this is overkill.

Fred

Put your hand on the riser. You can feel the cold water when it get there.

makinsteam

Awesome, thanks!

Hap_Hazzard

Fred said:

Put your hand on the riser. You can feel the cold water when it get there.

How can you feel it through the insulation? ;-)

Hap_Hazzard

I've mentioned this before, but when I had to replace my rotted out wet return, it was clear to me that the worst of the rust damage was on the outside of the pipe. I think at least part of the reason was that water had been left in the system year-round.

When the temperature is on the rise, the water-filled pipes stay cold because of the cold water inside, so you get warm, damp basement air meeting cold pipes, so moisture condenses, and oxygen is abundant.

So, if you have a wet return and a damp basement, and you intend to keep water in the system, consider insulating the return or painting it with a good rust inhibitor. Running a dehumidifier might help too, but if the piping is behind drywall, it's going to get damp.

ChrisJ

All of my water filled pipes are copper so it's never been a concern, but I've never seen them sweat even when my basement was around 80% RH (pre-dehumidifier days).

I don't think I've ever seen the air in my house change fast enough to cause such a thing?

Hap_Hazzard

Hatterasguy said:

What prevents the "cold" water inside the pipes from climbing up to room temperature (the air temperature at the floor level in the basement)?

Nothing. It's just that, while the temperature is rising, the temperature of the pipes lags behind the air temperature--considerably, due to the specific heats of steel and water. The condensation I referred to is a part of the process of warming the pipes. When the air gives up heat to the pipe, it can't hold as much moisture, so it leaves it on the pipes.

Hap_Hazzard

@ChrisJ ¯\_(ツ)_/¯ maybe there's something unique about my basement. I can't think of any other likely reason for the pattern of attrition I saw.

ChrisJ

Hap_Hazzard said:

@ChrisJ ¯\_(ツ)_/¯ maybe there's something unique about my basement. I can't think of any other likely reason for the pattern of attrition I saw.

Good, you keep it.
My house has enough weird stuff going on. Every time I start an easy project I end up hating life and it takes 10 times longer and twice as much money as expected.

I don't even bother opening windows / storm windows anymore because everytime turns into the Amityville horror with bleeding fingers. Ok, maybe not that bad but someone usually ends up with a headache or hurt something or other.