Condensate tank and now water hammer!

Steve Garson_2

As part of a major renovation, the condensate pipe that runs along the wall of room we are renovating has been removed and replaced with a condensate tank and pump. This is a single pipe steam system.

The attached photo shows the new tank.

Now, in mid cycle, there is loud hammer coming in what seems like the vicinity of where the new pumped condensate, which now comes from the ceiling and connects to the remains of the old condensate pipe that continues to the boiler. The hammer sound seems to be followed by the pumping of more condensate a minute or so later.

What did my contractor not do?

Thanks,

Steve Garson
Newton, MA

Brad White_203

What is

the purpose/need for the pump and what is the inverted loop/air trap before the inlet of the pump receiver?

Steve Garson_2

Brad:

The pump is needed because the condensate pipe was in the way of adding some showers and toilets.

Steve

Brad White_203

And the

inverted loop (air trap?)

There is a way to let gravity work without using a pump. An air loop over a buried section of wet return.

The Steam Whisperer (Formerly Boilerpro)

If this is draining the end of a one pipe steam main....

You'll need a trap on the vertical drain line and the return pipe will need to be able to return the water by gravity to the condensate pump.....not with a upward loop like it appears to have now. Also the steam main will need it's own air vent....F&T traps do not vent air very well.

Boilerpro

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Steve Garson_2

Brad:

I'm not sure what you mean.

Steve Garson_2

The plumber said the upward loop is to prevent steam from entering the tank and being released by the tank vent that is open to the air.

The hammer sounds are twenty feet downstream of the output of the pump. Not before the tank.

Brad White_203

Try this

detail...

Steve Garson_2

Brad:

Now I understand. This would require chipping out the concrete floor to lay the return, which is more costly than we would like.

The hammer sound seems to come from the area near where the new pumped return enters the return line near the floor.

We're close to doing plaster and I am concerned that the plumber may think he knows what he's doing, but doesn't.

Any other thoughts? Or does this setup always result in hammer?

Brad White_203

Chipping Concrete

and digging a trench is usually less money than buying and installing a condensate pump and the operating costs are borne by gravity... Oh well- next project!

I have used pumped returns into the return near the boiler at the base but only on boilers without a Hartford Loop. This is the problem, I bet.

You know the edict to connect the Hartford Loop with a close-nipple? To make that as short as possible? The idea is that you do not want the condensate to gain any velocity as it heads into the equalizer where it collides with steam. Hammer time.

Now, when you pump it, it does not matter how short that nipple is. You have slugs of flow when the pump runs. That is what I see. Does it coincide right at pump time or is it sporadic?

And that inverted loop? If it is a wet return already, there ought not be steam in it. If there is, charge admission under a pledge of it healing the sick.

rich pickering

I spoke with my general contractor and he told me that the problem is that the plumber used the incorrect type of trap and a replacement will solve the problem. Does that sound reasonable?

The pumped condensate rises to the ceiling, crosses along the ceiling for roughly twenty feet and then goes back to the floor to connect to the return to the boiler feed tank.

There is condensate drip that goes to the return next to the pipe from the condensate pump. Should this drip have am F&T trap where it connects to the main? Might this be the cause of the problem?

Michael Wilson

Bathroom Drip

Is this piping new or recently altered?

Others can chime in here, but I didn't think you want to change direction on a drip until below the water line of the boiler.

Correct me if I'm wrong fellas!


Mikey

rich pickering

The unpainted pipe was installed yesterday.

Jim Bennett

After the condensate.....

is pumped across the ceiling, and starts traveling downward towards the floor (after the pump shuts off) Could it be pulling a slight vacuum and flashing to steam?

ttekushan_3

I was thinking about that hartford too.

I think the hammer precedes the pumping by about a minute. If the height of the nipple wasn't quite right to begin with, it might not have mattered based on the water line in the piping. With the pump, the water level has a chance to fall further just before the pump goes on.

This is if my understanding that this is a wet return.

Do you suppose a float vent like a hoffman 75 on the line elevated line between the pump and the boiler would be helpful, like the vent on top of a false water line loop? The location of the hammer threw me since I fully expected it to be at the end of the main just before the pump goes on because of the large inverted loop feeding the condensate receiver. If air collects there, it can air lock and allow condensate to rise near the end of the steam main. On false water lines, this is where the float vent is usually located if I recall correctly i.e. at the top of the inverted loop.

I can imagine two unvented loop seals could cause a problem.

Does the check valve on the pump outlet line ever chatter?

The Steam Whisperer (Formerly Boilerpro)

That's what I was thinking...

You probably need a vacuum breaker on the pump outlet at the ceiling just above the condensate pump. Dan H talks about it in his books.

Boilerpro

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rich pickering

The water isn't flashing to steam after being pumped. The hammer occurs a couple minutes before a pump cycle.

Brad White_191

Then maybe

it is not the pump?

I cannot see anticipation from an inanimate object.. "let's see... pump ought to run in two minutes, why don't I make some noise?"

Thinking aloud here, what would proceed a pump running is low water in the boiler usually. What is the waterline doing at that time? Is it dropping below the Hartford Loop level and introducing steam out the back-way? A thought.

rich pickering

Brad:

Thanks for your interest. The return feeds a proper boiler feed tank that has been in place for years and works fine. It sits around thirty feet from where the overhead condensate run connects back to the return near the floor. So I would expect that the return is full of water all the time.

I am wondering if the new drip from the main is pushing steam into the return and perhaps some of that steam is rising into the new line from the pump. The two pipe connect to the return next to eachother.