Hammering in basement apartment after raising return lines

shampoo

[edited]
This one pipe (though it's two in the basement?) system is in a 3 story apartment building built in 1920. In 2012 the wet return lines buried in the concrete were abandoned and new return lines were run on top of the floor of the garden apartment. Steam feeds down from the mains in the ceiling to the top of the radiators and also directly into the return line. The return lines (east and west) also drop from the ceiling. The radiators sit on 15" platforms and there are no steam traps on the radiators. The radiators in the west side have valves [vents], but the radiator in the east side has a plug. [When the valves on the radiators are open the radiators get hot. The valve on the radiator near the hammering is currently closed, though the room gets hot enough because of all the uninsulated steam piping in the ceiling and walls. There was at one point a second radiator on the east side, but it was removed several years ago because the room it was in gets warm without a radiator]. The radiators get plenty hot [when their valves are open].

[The boiler cut in is set to 2psi. The pressuretrol is set to 7psi]

In 2012 a condensate pump was added instead of running a return above ground across the lobby. The problem is that when the return pump comes on the pipes near the radiator in the east half of the building hammer. When the pump turns off the hammering stops.

In 2017 a new boiler was installed. I do not know what the water level of the old boiler was, but the new boiler's water level is 36" above the floor of the basement floor. In the pump room the return from the east half of the apartment comes in about ~10 [inches] below the floor level because it is routed under the lobby floor. The return pipe from the east [west] side of the apartment comes in at roughly floor level.

My best guess right now is that the artificial water level in the garden unit is too low. The pump comes on and a water seal near the radiator is broken and there is hammering. My best guess on fixing this problem is to raise the water line. I would like to hear what others think is the cause of the problem and how to fix it.

Radiator that bangs [on the east side] Steam enters on the top left. Connects to return on bottom right


Radiator that bangs [on the east side] - Steam comes from the ceiling, branches into radiator then continues down to floor & connects with return


Radiator on the west side that doesn't bang


Wide view of pump


Closeup of water seal? About 8" above the floor


Top pipe is the return from the west side & enters at the floor level of the garden unit. The bottom pipe is the return from the east side. The bottom pipe runs under lobby floor for about 4 feet before returning to floor level


Closeup of the condensate receiver. Is it properly vented? It's not designed to be pressurized.

Jamie Hall

I suspect your best guess may be right. The fix, however, is not -- at least to me -- obvious at the moment.

But let me ask: By valves you mean radiator vents, I presume? And there are none on the east side radiators, which is where you hear the hammering? But all the radiators, east and west, heat?

If that is so, where do the east side radiators vent? They have to, if they are heating, after all. There is a mistyping in your description which rather muddies the waters... you say " the return from the east half of the apartment comes in about ~10 below the floor level because it is routed under the lobby floor. The pipe from the east side of the apartment comes in at roughly floor level.". Which is confusing. What is the relationship between the elevation of the return from the east, hammering, side, and the water level in the condensate tank into which it empties, which is vented.

Can you possibly make a sketch showing the piping in a side view, and the water levels?

shampoo

Thanks for your response Jamie. I edited my original post to fix the problems you mentioned.

What is the relationship between the elevation of the return from the east, hammering, side, and the water level in the condensate tank into which it empties, which is vented

The pipe from the east side is about 2" above the bottom of the condensate tank and about 8" below the top of the tank. If it isn't clear from the pictures the return from the west drops down to tie into the return from the east then they have to travel up a 21" vertical (about 10" above the the top of the tank) before entering the tank.

I should also note that the vent was added in the summer of 2020. I do not believe the tank was vented previously (venting the tank did not fix the hammering)

I will work on a side view sketch of the return pump and near pump piping and post tonight.

shampoo

@Jamie Hall Please see my drawings. I didn't include exact dimensions on in the condensate pump drawing, so please let me know if there is an important dimension I omitted.

Condensate pump



Radiators

Jamie Hall

Let me think about this one. I think I see what's happening, but... I need to think about it.

motoguy128

The radiator without a vent I assume uses a water seal as the trap. IF the system is running at 2psi, the pump might drop the return to atmpspheric and the seal is removed (2psi = 5’ seal).

I’d start by turning the pressure down to 0.5 cut in and 1.5 cut out or as low as it will go.

The Steam Whisperer

This is a job I have been out to at least 3 times and the condo association have always gone with someone else....giving the other contractors my design information. The last time I didn't give them any information on how I was going to solve this problem and it has stayed unresolved for 4 years. I believe 2 or 3 unit owners have been suffering with the issues since the work was botched with the " cheaper solution".

Jamie Hall

Ah. Thank you, @The Steam Whisperer . That sort of sheds a different light on it, doesn't it?

shampoo

I’d start by turning the pressure down to 0.5 cut in and 1.5 cut out or as low as it will go.

@motoguy128 thanks for the suggestion

shampoo

@The Steam Whisperer (Formerly Boilerpro) indeed! I'm not here to disparage the contractor that installed the new return lines in 2012, or the condo's board as I don't know the circumstances surrounding their decisions in 2012. To the contractor's credit in the last 8 years they have tried to fix (and succeeded, to some degree) the issues that have popped up since their 2012 work, free of charge. The only remaining issue that I'm aware of is the one described in my original post.

There is a new owner in the garden unit that is being motivated by a mother & 3 month old baby that are trying to sleep (and succeeding, to some degree) in the room with the water hammer. I do not believe the previous owners tried to sleep in the room with the water hammer, thus the problem went unaddressed until the new owner tried to sleep in this room.

That said, I have seen all the quotes from 2016. In 2016 there was banging in the garden and at least one other unit. The condo's board solicited bids to fix the problem, and the bids included fixes such as: installing traps on radiators, installing traps on return lines, lowering the condensate pump. The condo's board went with none of the bids because the contractor that originally installed the system came out and did something free of charge.

I'm not convinced that traps would be useful on the radiators, and I'm also suspicious that lowering the pump will fix the problem. This is of course assuming that the return lines are meant to be wet returns. If I'm correct then I would also think adding a false water line near the return pump would help fix the problem. Of course I am not confident in this assessment, hence why I have come for help. The fact that @Jamie Hall didn't suggest this initially makes me think that I may have gotten it wrong.

Jamie Hall

You may have multiple problems with that setup. One, rather obvious one, however, is that with the very low head available on the basement radiators you are almost certain to need some traps on the system. Gravity can only do so much, and steam passing into a return raises havoc.

And if @The Steam Whisperer has looked at it and made suggestions, I'd certainly not be one to second guess him. He's forgotten more than I've ever known about steam. One of the best out there.

shampoo

@Jamie Hall, thank you for your recommendation. I came here hoping to get a better understanding of the system to improve the chances this is fixed this season.

@The Steam Whisperer (Formerly Boilerpro) is there enough information here to jog your memory and fill in any blanks about the work since you were at the building last? Either way do mind giving me a call?

nicholas bonham-carter

I would see if boilerpro would be able, for a fee to provide the plan for rectifying changes to the system, which could be given to the contractor who has been on this job, and he can make those changes on his dime.
As Timco says, “steam heating isn’t rocket science-its a lot harder”—NBC

Neild5

Some how you need to just get the board to bite the bullet and hire @The Steam Whisperer and let Dave fix the issues.  He just installed a new boiler in the condo building I live in and I am extremely happy with the workmanship and quality of the equipment.   You can tell the dedication to his work, the quote was seven pages long.

JohnNY

shampoo said:

@The Steam Whisperer (Formerly Boilerpro) is there enough information here to jog your memory and fill in any blanks about the work since you were at the building last? Either way do mind giving me a call?

You mean @The Steam Whisperer should call and give you more free advice because your building hasn't wasted enough of his time and money yet?

shampoo

@nicholas bonham-carter I like this idea!
@Neild5 thanks for your recommendation

@JohnNY Thanks for your concern. I spoke to Dave last week and asked him to come out (at my expense) to see what changed since he was last here. I'm not looking to waste anybodies time.

I will unfortunately need two quotes for this sort of work in my building, so I want to make sure the second contractor (that I from find-a-contractor/) provides a reasonable bid. I ultimately do not get to choose who does the work.

Jamie Hall

Now you are making some progress, @shampoo ! I hope your condo board doesn't cheap out... as a friend of mine says, you get what you pay for. A suggestion: if you can do it, ask the bidders to warrantee the work as part of the bid: no cure, no pay.

nicholas bonham-carter

This is a difficult time to get the undivided attention of any steam pro, with winter just around the corner, so waiting for a second estimate may be very time consuming.
Your garden apartment dwellers may need a two-month supply of earplugs.
If one of the condo board members has a heart attack, will he have the ambulance stop at several hospitals for quotes on the services they offer, hoping to choose the cheapest one?—NBC

dopey27177

When the underground return was replaced with an above ground dry return the water seal provided by the wet return was lost. That water seal prevented steam from the other dry return from entering the return side of the part of the system that now has banging in it.

The cure for that is to make a false water line in the affected return piping. The false water line (will mimic the now removed underground wet return).


Jake