NYC Apt Renter--Hopeless Knocking Pipes?

lifeinthebigcity

Friends, Romans, etc
Moved into my fairly nice apartment in August after having lived in another steam-heated apartment in Manhattan the year prior. In my old place, the radiator would clang maybe once a night in the winter. After living there a few months, and armed with a white-noise machine, the sound didn't trouble me often. Now that the heat has kicked on in my new place, I'm confronted with a fun NYC sound I haven't heard before: whenever the system gets flooded with fresh hot water, there is a loud, regular knocking from the floor beneath my radiator. 2-3 times a night the knocking will persist for a couple minutes, and despite my white noise machine and fan, it rouses me out of sleep. I'd like to sleep consistently this winter.
It's definitely a pipe beneath the floor and not my radiator itself--when the knocking starts, I put my hand on the wood floor and I can feel it vibrate with the sound. The radiator, on the other hand, doesn't vibrate or react at all. Therefore I assume shimming the radiator and tilting it wouldn't necessarily help in this case.
Am I SOL y'all? I'm hoping I'll be able to adapt to the sound and tune it out eventually, maybe...

JUGHNE

If the pipe goes to your radiator valve and is a horizontal run under your floor, you might be able to lift the valve end of the radiator 1/2" and also raise the vent end the same amount perhaps 1/4" more for good slope. This sometimes works.
Don't go overboard on raising force.....maybe a little at a time.
Old piping etc.

lifeinthebigcity

Ooooh that's a good idea! I'll look into that, thank you

ethicalpaul

> whenever the system gets flooded with fresh hot water

Curious what you mean by this. This is a steam system?

lifeinthebigcity

Yes it is--I misspoke. It's very typical NYC steam heat!

ethicalpaul

I like @JUGHNE 's advice, it may help. A 2x4 can be used to lever it, but be careful and go slow (like 1/2 inch per day) and be ready to hide your tools if anything goes wrong! Use shims or pieces of 1/4" plywood (flooring samples work great) to put under the radiator feed and keep the valve side a bit lower assuming this is a single pipe radiator.

I would love to know the pressure that the system is running at (it should max out at under 2psi probably) but it may be hard for you to get or affect that.

lifeinthebigcity

The radiator is already raised--there are several wooden blocks under the feet, raising it already about 5 or 6 inches off the floor (this is the only radiator in the apartment in this position). Does this change anything? I'm having a hard time posting a photo sorry!

SlamDunk

if a 1/2 inch is good, 6" MUST be better!

ethicalpaul

Someone might have already tried this suggestion without success.

JUGHNE

Probably was a replacement rad. Is it of different design than the others.
IIWM, I would try the added shims.

Yellow header above may help you post pictures.

SlamDunk

I wonder if raising it that high created high and low points in a horizontal run.