Pitch of supply and return lines in a two-pipe system

Saldanah

Hi,

The return lines in my apartment are pitched correctly, but I noticed a couple of runs of supply line where the pitch is going the wrong way (probably from sagging). For cases of water hammers / banging, would the incorrectly pitched supply lines be a factor? Or is it just the return lines that carry the condensate that could cause water hammers when incorrectly pitched?

Thank you.

Jamie Hall

Poorly pitched or, worse, sagging supply lines are a much WORSE source of banging than dry returns — although those can bang too. Rehang and repitch them!

Saldanah

Turns out those improperly pitches lengths are not activated. They are cold to the touch while the banging continues.

ethicalpaul

They could be cold to the touch because standing water is condensing "killing" all the steam that tries to go there, causing the banging as it does so. They might not heat up for a long time.

Saldanah

The sections of out-of-pitch pipes that are visible in my unit drop down from the radiator above, and go horizontal in my unit. That is where we spotted the incorrect pitch. The radiators in the apartment upstairs are almost never used. So that pipe length is cold (supply and return sides). As a complicating factor, the radiators in that upstairs unit have Danfoss valves (the only unit that does) but given that those radiators are always turned off we are not suspecting the outlier valves or the pitch to be the issue. The banging often appears with the main return lines around that space vibrating at the same time, so one would think the valve and the pitch are not behind the noise? Puzzling and frustrating.

EBEBRATT-Ed

Any pipe that can get steam or water in it weather used or unused has to have the correct pitch. Shutting it off at the radiator doesn't count they still need pitch because steam/condensate can get in the pipe.

Saldanah

Wouldn't the temperature change somewhat when steam/condensate gets into the pipe? Plus return lines banging when a section of supply line that is cold to the touch is out of pitch?

ethicalpaul

Yes, if steam was getting to some standing water, you would see those pipes get hot from the main to the sag spot. If the pipes are stone cold all the way to the main then I would agree with you they are blocked and not allowing any steam in them. The banging must be somewhere else as you said.