Renovation Rerouted Steam Pipes

Jzik · February 2021

I am in the middle of a home renovation and my plumber decided to reroute some steam pipes that used to be exposed outside the walls to inside the walls. The old way, when they were outside the walls, the take-off pipes came off the main in the basement at a 45 degree angle and then the risers basically went straight up to the second floor radiators. Now that the pipes are in the wall, there are a lot of 90 degree elbows in order to navigate the wall space. The plumber recently turned the heat back on and I am getting crazy loud water hammer banging. I’m trying to figure out the problem and I’m wondering if it might be caused by all of the turns in the new pipes caused by the elbows? Or do excessive turns not really matter as long as everything is pitched and sized properly?

Jzik · February 2021

As an example, this pipe comes up from the basement (there are already some turns in this pipe in the basement right below this area that I don’t have a picture of at the moment)

Then it goes up and splits in two. The left pipe goes to a bathroom and the right pipe goes to a bedroom.

Then, here is the long horizontal run to the bathroom. I estimate the horizontal run is about 15 feet.

Jzik · February 2021

I forgot to add that I have a one-pipe counter-flow system.

Jamie Hall · February 2021

Unless your plumber got the pitch on every single one of those horizontal or almost horizontal runs correct -- for counterflow, 1 inch in 10 feet or more (a lot more for a shorter piece) -- it's going to bang. As you have found. In each of those pictures I can see -- even without a level -- at least one section of pipe which is going to bang. Guaranteed.

Sorry about that.

Hap_Hazzard · February 2021

Maybe your plumber doesn't understand that steam pipes in a one-pipe system are used for supply and drainage.

ethicalpaul · February 2021

At least they aren't copper

kenlmad · February 2021

In addition to the lack of pitch mentioned already, all the new iron pipe and fittings may be contaminating your boiler water with the residual cutting oil that is now being "rinsed" off the insides of the new iron and carried back to the boiler with the condensate.

A proper boiler "skimming" process (or multiple skimmings, as needed) will remove the floating oils from the boiler.

JUGHNE · February 2021

So your steam main is counterflow? Hopefully it has maintained its slope, and more so, still has the take off at a 45 not a 90 on the actual main pipe.

According to Dan's book, if a horizontal run-out is longer than 8' and if you can't get 1/2" per foot back to the main then you should increase the run out by one pipe size. (1/2" per foot turn out to be some serious slope).
If the repiping added some length to the run out it could be beyond these parameters.
I have noticed on old systems that they may have taken some sizes/length right out to the limits, exceeding them might cause problem.

Your second picture shows a fairly lengthy run out off of a tee, It looks level at best....hard to tell.

As mentioned you should skim the boiler of oils a few times to see if it quiets thing down.

EBEBRATT-Ed · February 2021

@Jzik

I wouldn't close in those pipes until you get it to quiet down.

Counterflow is certainly problimatic.

If the pipe can't be pitched properly due to not enough room you may be able to drip it to a wet return in a couple of problem areas

KC_Jones · February 2021

What size pipe was used for all this? If he dramatically increased the pipe runs, it may have been a good idea to upsize the pipe.

It appears you are feeding 2 rads with the single run, was it always like that or did both rads have their own feed off the main prior? If they used to have independent feeds, then I will reiterate my first comment.

I circled a 90 elbow prior to what you mentioned is a 15’ run, so it basically impossible for that to have slope as it should. He should have used a double 90 to create a swing joint to give slope.

One final question, did you tell the contractor about the banging, and what have they proposed as a solution?

Renovation Rerouted Steam Pipes

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