F & T trap configuration

michaelmiracle

I work in a school that is 100 years old and has a steam heating system. I have been replacing all of the steam traps this summer. This last F & T trap is in the crawlspace under the building. I don't see how it can work if the condensate line is above it, as pictured. Wouldn't it just flood until the level reaches the height of the highest turn in the pipe?
I don't see a way to reroute it since the condensate line is above the steam line at this point in the run.
Am I missing something?

Jamie Hall

If the atmospheric vent is closed when the float rises, pressure in the steam main should push the condensate up to the return. But... that assumes one has enough steam pressure, so this is one of those cases where there is a definite minimum pressure for the system to work. From the mark 1 eyeball the rise is about two feet? Then you'd need 1 psi.

EBEBRATT-Ed

It is actually piped the way it is supposed to be piped except there should be a check valve between the trap discharge and the return pipe. The check should be down low by the trap.

Since the steam main is below the return line the trap has to lift the condensate to the return line . It does this by steam pressure. 1 Psi will lift the water about 2'. The condensate goes into the top of the return line as it should.

This arrangement is very common but is avoided when it can be avoided for two reasons:

The trap can freeze if in a cold location and the trap fails or the boilers go down and no steam is available and.....You have to run with enough steam pressure to lift the condensate

Mad Dog_2

Michael...may I suggest two books by Mr. Holohan, our Founder, that any Steamfitter or plumber working with The Steam must have and read:  "The Lost Art of Steam Heating" & "Pocket full of Steam Problems & Solutions."  They cover all these scenarios you'll see & real neato ways to make them work.  Mad Dog 🐕 

michaelmiracle

Thanks for the help and explanations. I do have the 2 books and read the sections on F&T traps but didn’t get that the system would allow steam pressure past the trap. I thought the idea of the trap is to keep steam out of the condensate line. 

Jamie Hall

michaelmiracle said:

Thanks for the help and explanations. I do have the 2 books and read the sections on F&T traps but didn’t get that the system would allow steam pressure past the trap. I thought the idea of the trap is to keep steam out of the condensate line. 

This is true -- a very small puff of steam may escape, depending on the exact geometry of the float and all. Very small. Not to worry.

EBEBRATT-Ed

@michaelmiracle

You are correct the steam is supposed to stop at the trap and it does but a little flash steam always gets by. But that has no part in what is happening here.

In your case the steam drops down to the trap. As the steam condenses it changes to water. The trap senses water and opens up. The steam pressure from the main pushes the water up and into the top of the return line. Once the water is out the trap senses steam again and closes.

Its important to have a check valve in the Trap discharge line to keep condensate from coming back into the trap backwards. And discharging the condensate into the top of the steam return line (the bottom has water in it) helps with this as well.

michaelmiracle

I'm coming back to this thread for more on the same trap. The piping sprang a leak and I need to take it apart to fix it. As I look at it it is located right after where the steam and condensate pipe make a 90 degree turn. It is a low point in the line with 30' or so on either side. So water is collecting in this corner and making problems. Pipes are corroding and causing leaks. I suspect the condensate is not moving out of the steam pipe enough to handle it being at the low point.
I don't see that I can raise the pipe, it goes through a few brick walls so probably has always been this way.
The piping is reduced from 1" coming out of the steam pipe to 1/2" before going into the trap and back out to the return. I'm thinking to take it up to 3/4" or even 1" pipe. I believe that would help with the pressure of the steam that needs to push this condensate up to the return. Larger pipe translating to faster velocity of steam. Is my thinking on this correct?
I'd also add the check valve as suggested.

EBEBRATT-Ed

Just fix the leaks and add the check valve and leave the piping configuration as is.

Steamhead

michaelmiracle said:

I'm coming back to this thread for more on the same trap. The piping sprang a leak and I need to take it apart to fix it. As I look at it it is located right after where the steam and condensate pipe make a 90 degree turn. It is a low point in the line with 30' or so on either side. So water is collecting in this corner and making problems. Pipes are corroding and causing leaks. I suspect the condensate is not moving out of the steam pipe enough to handle it being at the low point.
I don't see that I can raise the pipe, it goes through a few brick walls so probably has always been this way.
The piping is reduced from 1" coming out of the steam pipe to 1/2" before going into the trap and back out to the return. I'm thinking to take it up to 3/4" or even 1" pipe. I believe that would help with the pressure of the steam that needs to push this condensate up to the return. Larger pipe translating to faster velocity of steam. Is my thinking on this correct?
I'd also add the check valve as suggested.

That's always a problem with this setup. Is there any way you can remove the cap on the dirt pocket and run a line from there back to a wet return or boiler-feed tank?

michaelmiracle

Steamhead said:

That's always a problem with this setup. Is there any way you can remove the cap on the dirt pocket and run a line from there back to a wet return or boiler-feed tank?

It's possible but above my pay grade. I'm not a plumber. I could look into adding that over the summer.