Steam Pipe pitching

Steamheatnovice · April 2021

Hi, I'm a steam heat novice looking for some advice. I recently had a section of my main supply line replaced due to a pinhole in the cast iron piping. Seemed there was a lot of water built up in the section of piping and the pitch is not correct. From the header on my boiler there is a pipe that leads to the main supply pipe. My question is what direction should the pitch be on the main supply pipe, should it be "uphill" from the boiler in the direction of the flow of steam so any condensate can flow (downhill) into the equalizer? I've had conflicting plumbers say one way or the other. My header is 2ft from the top of the boiier, then there is a pipe that goes vertical and connects to the main supply line. Is it OK to drop that vertical pipe say an inch to correct the pitch in my main supply line? One plumber tells me no that has to be kept a certain height from the header while another says it should be OK to drop a few inches (circled in red below) to allow the pitch in the main supply line be downhill toward the boiler allowing condensate to feedback into the boiler.
Sorry for the novice question. Any feedback would be greatly appreciated. Thanks in advance!

KC_Jones · April 2021

It appears you have a parallel flow system. the first elbow that you circled should be the highest point in all the main piping and is should be sloping down from there at an amount not less than 1" per 20' of pipe run. More slope is fine, less not so much.

Your assessment of bad pitch and water laying around would be backed up by the fact that you had that pipe get pinholes in it. Steam carrying pipes that drain the condensate away freely, roughly speaking, should take many generations before they have problems like that. Many of us on here have original piping from the system install still going strong. Pipes below the water line are a different story.

Jamie Hall · April 2021

Since I see no sign of a drip on that steam main, I agree with @KC_Jones . The entire steam line -- from that elbow you circle at the top of the riser -- to the very end where there may be a drip should slope at least 1 inch per 20 feet away from the boiler. Now to verify that before you start changing pipe, check the pitch of the rest o the steam main, and look to find a drip to a wet return somewhere.

JUGHNE · April 2021

All steam piping should be sloped such that when not steaming all water would drain back to the boiler. This means the main should drain back thru the return at the far end of it.
Also run out pipe to radiators should also drain back, if 1 pipe system they need more slope than the main as they are counter flow, that is steam up and water back down same pipe.

The return pipe at the boiler should be the lowest horizontal pipe in the system.

It looks possible that whenever that boiler was installed they may have pulled down the main so you lost some of that slope.

Is your new pipe over on the left side of your pictures?
What does the end of the main to return piping look like?

Also your boiler piping lacks swing joint 90's on the header.
If you look in the install manual you will see what I mean.

Steamheatnovice · April 2021

Thanks so much gents. As @KC_Jones mentioned, I think I have a parallel flow system. So at the end of the main supply there’s a U turn to smaller return pipe which lead back to the boiler with a main vent. Not sure what you mean by drip? End of the main to return is below. I also showed where the bow is in the main and where the pinhole developed. What would be the downside of dropping the riser from the header allow the pitch from the main back to the equalizer/boiler?

Image: https://us.v-cdn.net/5021738/uploads/editor/2v/bs95bfy0sa9y.jpg

Image: https://us.v-cdn.net/5021738/uploads/editor/af/t0rtlkszrsf2.jpg

Image: https://us.v-cdn.net/5021738/uploads/editor/4l/6tlhvpyg2bjy.jpg

JUGHNE · April 2021

If you bring the water back to the boiler thru the steam main then you have colliding steam and water. This will lead to possible water hammer and cause wet steam which leads to a variety of problems. The wet steam will throw more water up into the main compounding issues.

If you leave the bow/sag in the steam main there will be water standing in the dip.
That can cause water hammer as the steam hits the pool of water.
Also water standing in any steam pipe will rot out the bottom producing pin holes as you now know. As said above the entire piping system needs to drain from the top 90 above the boiler to return to the boiler.
This has been known for over 100 years, anyone who implies otherwise to drop that 90 2" down is not giving good advice.

Also the horizontal header above the boiler should slope to drain to the equalizer drop pipe.

Jamie Hall · April 2021

You really do need to correct all the pipe slopes so they are correct, including that bow. Also, check all the slopes of all the radiator runouts and make sure they are correct (if this is one pipe steam, they all should slope 1 inch per 10 feet back to the main). You will probably have to play with the pipe hangers to get it right.

Pulling that new bit by the boiler down to get it to slope towards the boiler will give you nothing but trouble.

retiredguy · April 2021

Another thing I noticed and I would ask the residential guys on this site, is the flue pipe correct? It looks to me as if the flue from the water heater "tees" into the furnace flue with no increase in the size going to the chimney. Is this correct or should the "tee" be a reducing tee say 7" at the chimney end and 6" for the furnace and 4" for the water heater. Just asking.

EBEBRATT-Ed · April 2021

@Steamheatnovice

Chances are when the pipe was originally installed it was pitched properly.

Chances are that when the boiler was replaced they cut the pipe loose from the old boiler and let it sag.....never raised it back up so part of it is pitched wrong

You could cut the riser pipe coming out of the tee above the boiler and replace it with two nipples and a union and increase the total length

Steam Pipe pitching

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