To drain, or not to drain, that is the question.

2wheelinfool

Watching youtube vids, I hear conflicting advice regarding flushing the boiler. One expert says you can drain and flush weekly to keep sludge at bay. Another expert says you should avoid draining because the makeup water contains oxygen that promotes rust. Instead, treat boiler with a solution to raise pH and keep the lower oxygen water in the system to slow oxidation rate of system components.

What do you all think?

EdTheHeaterMan

Keep the water in there on a closed system.
Open system needs to be flushed as needed to remove the buildup resulting from the oxygenation of the ferrous materials in the boiler, pipes, pumps, and the like. The as needed is depending on each system and weekly might be too much.

Flushing a float type LWCO weekly is a good idea, but flushing the entire boiler is probably overkill on a major scale.

Do you have a specific boiler in mind? What is it used for and what type is it? Open or Closed... Hot Water or Steam... Space Heating or some commercial process application?

With some more particulars, we can give better advice.

Yours Truly,
Mr.Ed

EBEBRATT-Ed

@2wheelinfool

If you have a float type low water cutoff you should blow that down weekly.

Other than that I would drain , flush and skim the boiler once a year.

When you add make up water run the boiler to steam it to drive out any oxygen

2wheelinfool

@EdTheHeaterMan , this is a single pipe steam residential heating application. Not familiar with open vs closed terminology, but I would guess open, since the system has thermostatic air vents at each radiator. There are 7 radiators on the first floor and 4 on the second floor. Here are photos of the boiler. The LWCO looks to be a non-mechanical type, correct?

2wheelinfool

@EBEBRATT-Ed why skim every year? How does oil get into the system?

JUGHNE

Looking at these and your other pictures on the other posting, it looks like you have a main steam line vent at the top of drop pipe that connects to the HL wet return.
Can you post a good shot of that vent and and brand and or numbers on it.
It is on a very small pipe up near the ceiling.

Jamie Hall

Your system needs to be flushed out -- at the bottom drains -- once a year at the most. Otherwise, on that system, there is no need to blow anything down or flush anything out at all.

Hap_Hazzard

I agree with Jamie, but would add that it's recommended to inspect and clean the LWCO probe yearly. I'm not sure it's really necessary to do it that often, but that's what they recommend. I let mine go for a few years, and when I finally did inspect it, it was like new, but a lot might depend on your water quality. Just be sure to use pipe joint compound instead of PTFE tape when you reinstall the probe, as the tape can keep it from making a good electrical connection. You can use compound with PTFE if you like, but don't use tape.

2wheelinfool

@JUGHNE here's the under capacity, probably 100 year old vent valve. Need to determine best approach to increase venting capacity. I think that 1/8 pipe into the main vent might be too restrictive. Should I drill and tap the bushing to 3/4", try and remove the bushing, or cut and thread the 1/8 riser and antler off two gorton no. 2's?

2wheelinfool

@Jamie Hall what's the difference between a flush and a blow down?

2wheelinfool

@Hap_Hazzard is it sufficient to do a yearly functional test -- drain down while running until LWCO actuates? Or is removal and visual inspection better, or more recommended than the functional test?

Jamie Hall

2wheelinfool said:

@Hap_Hazzard is it sufficient to do a yearly functional test -- drain down while running until LWCO actuates? Or is removal and visual inspection better, or more recommended than the functional test?

A blow down is commonly meant to refer to opening a valve long enough -- but no longer -- to remove accumulated solids -- sludge -- either at the bottom of the boiler (rarely done, and equally rarely required) or to clear the chamber of a float type low water cutoff. It can be, and in some ways is better for it to be, done under pressure -- though heating boilers should never generate enough pressure for that to be a consideration (a power boiler, now -- a blowdown can be rather spectacular!). For the latter, if done reasonably often, a gallon or so of water is usually ample. Flushing a system is more commonly used to a more or less complete change of the water, often (as in hot water systems) a much higher velocity flow through the system to get any lingering crud out.

JUGHNE

For the air vent, I would try to remove the bushing and replace it with a 3/4".
A warm weather project, soak it with PB blaster several times before trying.
Use 2 pipe wrenches.

2wheelinfool

@JUGHNE , would you heat the 2-1/2 elbow up with a torch as well?

JUGHNE

Show the bushing, not too close.
How long is your main?
From boiler to last connected radiator.

2wheelinfool

@JUGHNE I measured 670" of 2-1/2" pipe from the header to the drip leg where the main vent is located.

2wheelinfool

@JUGHNE I measured 670" of 2-1/2" pipe from the header to the drip leg where the main vent is located.

2wheelinfool

Another idea for removal: try an electric impact driver?

JUGHNE

Is your 2 1/2" pipe the inside diameter or outside?

I would spray it several times.
Impact good if you can find a 6 point socket that fits tightly, might even file the flats of the bushing it get tight fit.

I have cracked cast iron fittings just unscrewing nipples out of them.
I would wait for spring to do this for that reason.
If you had to "crack" that tee it would not be the end of the world as there is a union below on the HL, you would have to cut the water copper line.
56' of 2 1/2" main might justify 3 Gorton #2's or 2 B&J Big Mouth air vent.
I would change that bushing to a 1" for venting. Nipple up, 90 ellbow, nipple to tee, nipple to second tee. Raise vents up as high as possible. The horizontal manifold you build should point back towards the 2 1/2" so there is some slope to drain the manifold back to the tee drop.

You have 2 1/2 riser out of boiler, 2 1/2" steam main but....the reducing tee is concentric fitting....there will be a pocket of water sitting in that tee. The reduction should be on the vertical drop only.
May not be enough of an issue to worry about, tough to change now, may not be worth the grief.

Hap_Hazzard

2wheelinfool said:

@Hap_Hazzard is it sufficient to do a yearly functional test -- drain down while running until LWCO actuates? Or is removal and visual inspection better, or more recommended than the functional test?

It's probably a good idea to take it every year or two just to see what it looks like and to keep the joint compound from hardening. It's probably not worth draining the boiler just to test the LWCO, but if you're draining it anyway, you can test the LWCO by filling the boiler up with the power on and seeing if it lights. If you see water in the glass gauge when the burners come on you'll want to mark that on the glass, but usually it will come on before you see it. I think the rule of thumb is that the probe is good if the boiler works, because they generally fail open.

2wheelinfool

What are the failure modes? Scale buildup? Sludge buildup?

Jamie Hall

2wheelinfool said:

What are the failure modes? Scale buildup? Sludge buildup?

Probe type LWCOs sense the conductivity of the water between the probe and the boiler shell. So anything which interferes with that will cause them to fail sensing a false low water (such as just plain grundge building up on the probe). Poor installation may cause a similar failure, due to no conductivity between the shell of the probe and the boiler (such as might happen if someone uses tape) or, more rarely, a partial short which will cause a false high water reading.

Float type LWCOs almost always fail, when they do, due to the float hanging up in the chamber -- either stuck down or prevented from dropping -- by sludge, which you remove by blowing the chamber down. Once in a while the float will spring a leak and just sink.