Can you get water hammer with closed valve?

snootyusher

In my bedroom, in a 6-floor/24-unit coop with single pipe steam heat, I've got:

1) a capped-off steam pipe (presumably used to service a radiator when apartment was configured differently)
2) a vertical insulated steam pipe from floor to ceiling
3) a small radiator

They're all kind of lined up in a row; #1 is about a foot to the left of #2, and # is about a foot to the right of #3.

I'm experiencing hammer/knocking noises from the floor right around #2, even with #3 fully closed (also when it's open).

I'm getting a replacement vent on #3 today and am hoping that somehow solves it (going from a Honeywell TRV to a Vent-Rite #1), but considering the hammer happens even fully closed, I'm skeptical.

Any thoughts on what would be causing this, or next steps if the replacement doesn't work?

As a side note, I find that when I step on the hardwood floor around #2, I can sometimes sort of reproduce the hammer/knock noise with the pressure of my own step. I wonder if some kind of expansion/contraction is going on? Might be a red herring though?

Jamie Hall

Take a close look at how that vertical pipe goes through the floor. While one can, under some conditions, get a water hammer effect at a closed valve, it would be very different between open and closed. Expansion of that vertical pipe, though, could well produce a pretty loud sharp noise if its sticking and the slipping on a floor board. If the pipe is touching the floor anywhere around it, try pushing it over and slipping a piece of polyethylene plastic or similar (a piece cut from a milk jug works well -- if you can fine a milk jug these days) in where it touches and see if that helps.

snootyusher

Here are some photos of where the pipe meets the floor. Looks like a very old, very painted-over plate, also with some insulation shoved in there. It has some wiggle/give (both horizontally and vertically), but won't come loose (at least not without some force). Is it a good idea to force this thing open?

Also a video of me showing its movement: https://www.dropbox.com/s/8cv9hr1njpbjow7/PXL_20211028_155524825.mp4?dl=0

snootyusher

I managed to pry the escutcheon off, dusted away some disintegrating/powdery insulation, and saw this:



it really does look like what @Jamie Hall said- there's definitely some wood, just to the left of the screwdriver, that is in direct contact with the pipe!

I know you mentioned jamming some plastic in there but it looks like there's literally zero clearance...how do I shave back this wood safely to get the plastic in?

mattmia2

Is the floor tight all the way around it or is there a space on the other side? If it is tight all the way aroung your only real option is a narrow and sharp chisel and cut the end of the wood away or maybe an oscillating saw with a narrow, long blade.

It looks like someone was doing something with spray foam around that pipe.

snootyusher

It seems pretty tight all the way around. Gaps on the other side are filled up with that spray foam substance.

Unfortunately there's no give at all when I place moderate pressure against the pipe. Trying to not lean into it too hard, wouldn't want to make a disaster.

Would scooping out that spray foam be a mistake? I don't know what it's meant to do, or if it should be replaced (either with identical product, or something else). Getting it out of the way might at least gain me some purchase in order to chisel away a bit of space (I'm just a layman and co-op apartment dweller with no fancy tools like an oscillating saw)

snootyusher

Related, if you have a recommended chisel that would be a good fit for this job...please let me know. Would it be a woodworking chisel like this:

https://www.amazon.com/Tools-Marples-Woodworking-Chisel-M44418N/dp/B000RFYZLI

Jamie Hall

Someone didn't do you any favours at all, did they? Yes, I think that chisel would do it -- or a quarter inch. Learn to sharpen it... and take your time.

The bad news is there may be a subfloor under there...

snootyusher

Yeah, no favors at all is right. I'll pick a chisel up tomorrow and see how it goes. I think I've got a game plan here now. Thank you!

snootyusher

Perhaps dumb question- should I be chiseling parallel to the area I want to open up, or perpendicular? I'm thinking angle of attack- should I be chiseling *alongside* the pipe, or *facing* it?

Jamie Hall

snootyusher said:

Perhaps dumb question- should I be chiseling parallel to the area I want to open up, or perpendicular? I'm thinking angle of attack- should I be chiseling *alongside* the pipe, or *facing* it?

Not a dumb question at all. What you are attempting to do is to chisel the opening about an eight to a quarter inch bigger in diameter. So... I would set the blade of the chisel on an imaginary circle that much bigger, and cut down along that circle (actually, it will be a multi-sided figure, as the chisel isn't curved). Try to get a good cut straight down (more or less!); you'll be able to get -- if the chisel is goo and sharp -- perhaps an eighth to a quarter inch down (use a hammer). Use the chisel to pry out what has been cut. Rinse and repeat...