Thread: Double Traps

Ok olde time plumbing gurus.

I don't know if I'm running into the same plumber or if the practice was allowed back in 1988-89.
1) When were double traps made non-conforming.


2) In what year were expansion tanks/pressure valves required on the cold supply of water heaters? Seems every private well w/pressure tank system that I run into, brand new or older, is missing a water heater expansion device. Now, I understand where a water supply pressure tank could act as over pressure buffer, but I don't see in my 2003 - 2006 code info any exceptions for well systems. (maybe I'm blind or just tired. Up til 3:30 AM last night working on a report using new software)



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Originally Posted by Stuart Brooks

Ok olde time plumbing gurus.

I don't know if I'm running into the same plumber or if the practice was allowed back in 1988-89.
1) When were double traps made non-conforming.

Double traps in series are not allowed. You can have a double sink with a trap on each sink drain but the drain line can not have a trap, or you can have a trap on the line after the two sinks join. I don't know the year, but it should not matter.

2) In what year were expansion tanks/pressure valves required on the cold supply of water heaters? Seems every private well w/pressure tank system that I run into, brand new or older, is missing a water heater expansion device. Now, I understand where a water supply pressure tank could act as over pressure buffer, but I don't see in my 2003 - 2006 code info any exceptions for well systems. (maybe I'm blind or just tired. Up til 3:30 AM last night working on a report using new software)

If the system is a closed system it requires an expansion tank or a expansion relief valve. If one is not installed the pressure will build and something is going to leak. Most likely the TPR valve.

On a well system the back pressure might go back to the holding tank but the pump would prevent it from returning to the well. Again the dates do not really matter. I don't see that many well systems to be of much help.

Bottom line is that they are only required if the system has a backflow preventer, a PRV or anything that acts like a check valve.

Originally Posted by Scott Patterson

Double traps in series are not allowed. You can have a double sink with a trap on each sink drain but the drain line can not have a trap, or you can have a trap on the line after the two sinks join. I don't know the year, but it should not matter.



If the system is a closed system it requires an expansion tank or a expansion relief valve. If one is not installed the pressure will build and something is going to leak. Most likely the TPR valve.

On a well system the back pressure might go back to the holding tank but the pump would prevent it from returning to the well. Again the dates do not really matter. I don't see that many well systems to be of much help.

Bottom line is that they are only required if the system has a backflow preventer, a PRV or anything that acts like a check valve.

Thanks Scott.

Traps - 2003 IRC says cannot have 2 traps running into same drain arm
Like - double kitchen sink. Now, I admit I'm relying on code check book for that info.
This is labeled a NO-NO
SINK SINK
| |
PT PT (p-trap)
| |
+-----+-----+
|
| (drain arm)

And this is labeled as acceptable,
sink tail to sink tail to P-trap to drain arm.
SINK SINK
| |
| |
+----------+
|
PT
|
|
+----------- (drain arm)

That's why I was wondering about date and asking. The stated issue is venting and the possibility of one sink drain sucking out water seal from trap of second sink.

Stuart,

Hard to make out what you are trying to show in your post, but what I get from it, Scott is correct, you can have two sinks, each has its own trap, which go together and back to the stack.

You do not need to connect both sinks together 'before' a single trap.

Do you have a photo?

Originally Posted by Jerry Peck

Stuart,

Hard to make out what you are trying to show in your post, but what I get from it, Scott is correct, you can have two sinks, each has its own trap, which go together and back to the stack.

You do not need to connect both sinks together 'before' a single trap.

Do you have a photo?

No. not of the sinks in question. But I can scan the codecheck page.

So, you weren't a big computer user when all we had to "draw" with were ASCII characters and, of course, a monospace font. That was right after I quit rubbing 2 pieces of wood together to do math. Still have that old 1967 vintage K&E analog computer. I used to hang it up on the office wall so the new engineers could ask, "What is THAT?"

Originally Posted by Stuart Brooks

So, you weren't a big computer user when all we had to "draw" with were ASCII characters and, of course, a monospace font.

sink------sink
-|---------|
-|---------|
-pt--------pt
-|---------|
-|---------|
-|-_______|
-|/
-|
wall

Okie Dokie - The problem was due to me skipping over a little detail note.
Code Check says the IRC allows 2 traps to drain into a single trap arm but the UPC prohibits the practice. I only have to worry about the IRC.

Thanks!