Draining / Flushing a one-pipe steam boiler

Tolik

Hi, please help me understand what the best way would be to flush my system. I'm pretty sure there is a lot of sediment in the Harford loop and one (of two) return piping.

The boiler is surging like crazy and one of my second-floor radiators spewed brown water out.

Would draining it from the sight glass area or the lower right (there is a nut) be the best place? I can put a valve there and build pressure then open it up? I'm pretty sure there is a lot of sediment in the bottom pipes.

delcrossv

There should be a bottom drain . More pictures would be helpful

BobC

There may be a drain valve down low on the back. If there is just attach a hose and drain it to a floor drain or shallow pan, do this when the boiler is not hot. Drain - refill and drain a couple of times to get most of the crap out. Fill the boiler to it's normal level and see if that calms things down, you may still have to skim it there are oils in the boiler water.

Bob

Tolik

@delcrossv @BobC I wish I can say there is a drain valve or anything other than what is visible in the picture but there isn't.

I managed to drain it by removing the nut (and elbow) that is on the T in the lower right corner. The T was fully clogged. Using some elbow grease a coat hanger and shop vac I managed to clear it. 

Unfortunately in the process I also poked a hole in the pipe. Plugged it using JB weld. It's below the water line when the boiler runs that pipe never gets hot. I hope it holds. Eventually will need to replace all the piping of Hartford loop. 

delcrossv

Poked a hole in the pipe?
If they're that rotted, you need more serious intervention..

Seems the closest thing you have to a boiler drain is the system drain next to the pump.

Tolik

@delcrossv I was pretty surprised to say the least. The pipes are corroded. 

Waher

You need to have that pipe replaced ASAP. If it's that corroded it could fail catastrophically and the last thing you want is a boiler firing dry if the low water cut-off fails.

Big Ed_4

Your system is piped incorrectly .When I seen the pump installed in the only "X" position........ I backed out of the basement

The solids left behind are from steam leaks .....

Sylvain

BobC said:

[...] Drain - refill and drain a couple of times to get most of the crap out. Fill the boiler to it's normal level and see if that calms things down, you may still have to skim it there are oils in the boiler water.

Bob

You will have to refill/purge the hot water loop.
see:
https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

but I don't see valves to isolate the hot water loop for this operation.

edit
but maybe you have a heat exchanger instead of a direct hot water loop.

Tolik

@Sylvain there is no heat exchanger. Whoever installed the boiler, after hurricane Sandy and before I purchased the home, did a sloppy job.

Sylvain said:

You will have to refill/purge the hot water loop.
see: https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

I ran the pump while simultaneously filling and draining the boiler. I figured this method would drain and refill the loop with clean water. Was I wrong in doing so?

Tolik

@Big Ed_4

Big Ed_4 said:

Your system is piped incorrectly .When I seen the pump installed in the only "X" position........ I backed out of the basement

The solids left behind are from steam leaks .....

I had a leak in the dry return pipe two years ago. Then again this year. What you're saying makes 100% sense.

Not sure what you mean by "...installed in the "X" only position..."

Sylvain

Tolik said:

I ran the pump while simultaneously filling and draining the boiler. I figured this method would drain and refill the loop with clean water. Was I wrong in doing so?

Maybe be you get lucky but there are reasons to do it otherwise (like it is described in the link; including in which order to close the valves)):

- a circulator has only to compensate friction in the pipes; it is not supposed to push water above.
On the other side, city water has enough pressure to fill your loop up to a few floors above.
- city water will give enough flow to carry air back to the bottom. Low rate of flow will not do it.
- there must some sort of seal (water or valve) to prevent air to enter back in the loop; so the loop must be isolated if, while flushing the boiler, the water level doesn"t seal anymore the two extremities of the water loop. See the explanation in the link (in the second part after the part about heat exchanger).
drawings + text