Thread: Where is the P-trap for kitchen sink

These photos are taken from a 3-millions new house.
1. No high loop for the dishwasher drainpipe (the white plastic flexible hose).
2. No visible P-trap under this kitchen sink, but a cleanout is there. Is a P-trap underneath the board?

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P-Trap is not visible from this angle, however it may be visible by use of a camera from behind the rear partition. Or maybe there is an access door in the basement. If there is no access door below, simply note that a P-Trap is not visible. You also could remove the clean-out plug, and use a flashlight and or short snake to probe for a trap. Again, if you cannot verify a trap is there, note it and refer for plumber inspection.

- Can't see a trap, then there is no trap. Let them prove otherwise.
- Check local ordinance on the dishwasher drain into the garbage disposal, not allowed here.

Originally Posted by Daniel Leung

These photos are taken from a 3-millions new house.
1. No high loop for the dishwasher drainpipe (the white plastic flexible hose).
2. No visible P-trap under this kitchen sink, but a cleanout is there. Is a P-trap underneath the board?

Kitchen sinks traps are allowed to be below the floor in Canada.

Canada marches to a very different drum -- Notice the yellow ABS glue? That would be considered contraband in the lower 48; And the absence of a high loop and discharge into a disposal? Perfectly allowable under the Red Seal Code.

It's a very different world up there.

Hey, are these two kitchen sink traps acceptable?

The first Pic is OK
The 2nd is an S trap, not good

Originally Posted by Widdershins Saunders

Kitchen sinks traps are allowed to be below the floor in Canada.

Canada marches to a very different drum -- Notice the yellow ABS glue? That would be considered contraband in the lower 48; And the absence of a high loop and discharge into a disposal? Perfectly allowable under the Red Seal Code.

It's a very different world up there.

Correct, ABS glue has always been yellow in Canada.
Many but not all dishwashers have a high loop incorporated in their design, where the loop is clamped to the side of the unit.

Daniel, if there is no access to the trap, I would call it out. Should be accessible.

Originally Posted by Gary Winfield

Hey, are these two kitchen sink traps acceptable?

#1 seems to be OK, #2 is wrong, an "S" trap.

I see Rick beat me to it. Gary, didn't you take 'S" trap training at some point?

I threw these pics out for feedback. I did a ride along and the inspector did NOT write up the S trap. Are P traps primarily used almost ALL the time? He said as long as it drains and no leaks, he never writes it up.

Originally Posted by Gary Winfield

I threw these pics out for feedback. I did a ride along and the inspector did NOT write up the S trap. Are P traps primarily used almost ALL the time? He said as long as it drains and no leaks, he never writes it up.

S traps don't leak as a rule, and Yes the sink will drain. The problem can be siphoning of the water out of the trap. With no air getting back into the trap arm (drain end), the suction of drain water can draw all the water down the drain. Sewer gas (methane) will then leak up the pipe into the kitchen.
Always call out the S trap, or be prepared to hear something like "my friend says you should have seen that and now we want it fixed."

S traps were commonly used in older houses right? If you see one in an older house, do you call it out?

Yes John. Those really older homes also may have had and may still have a house sewer trap - an expensive correction and prone to clog/catch all sorts of collections.Without a house trap an S trap has the potential to back up with public sewer or private sewer or sanitary system gasses, both toxic and flamable/explosive.

Originally Posted by Rick Cantrell

The first Pic is OK
The 2nd is an S trap, not good

Technically, the 2nd is a running trap.

An S trap would be a vertical to vertical installation.

The last 90 degree change in direction makes this a running trap.

Still illegal, but definitely not an S trap.

Originally Posted by Widdershins Saunders

Technically, the 2nd is a running trap.

An S trap would be a vertical to vertical installation.

The last 90 degree change in direction makes this a running trap.

Still illegal, but definitely not an S trap.

Technically it is not a running trap.

It is more of an S trap, albeit a modified S trap.

A running trap has the inlet and the outlet of the trap at the same level, the trap in the second photo does not have the inlet and the outlet at the same level.

I used 'modified S trap' as an S trap does indeed go down (as that photo does, but the S trap continues to go down whereas the trap in that photo turns back horizontal toward (the vent?), thus modifying the S trap configuration.

Thanks for all the input. I WILL make certain that I write up ALL S traps.

Gary

Originally Posted by Gary Winfield

I did a ride along and the inspector did NOT write up the S trap... He said as long as it drains and no leaks, he never writes it up.

IMO: Find another inspector to mentor you, or just research, research, research for yourself, otherwise you are likely going to have to unlearn other incorrect "information" as well.

Back to the OP.
Was the plumbing visible below the floor level (crawlspace or basement)? The trap may very well be under the floor level.

Originally Posted by John Kogel

Daniel, if there is no access to the trap, I would call it out. Should be accessible

No, it does not need to be accessible.

Look at it this way; Are the traps for showers or bath tubs required to be accessible?

As long as the trap is not a union or a slip joint trap, then concealment without access is perfectly permissible.

This quote is not me. It is from a well respected inspector of many years.

Real s-traps don't siphon themselves dry; they never did and they never will. The men who designed them knew full well about the dangers of siphoning and they designed the s-trap so that an air break developed before the water could all siphon out. If you don't believe me, try it. You can't get a *real* s-trap to siphon dry. Siphoning is a phenomenon reserved for ersatz s-traps made from spare parts.

The real reason we did away with s-traps is subtler. If you've got a large slug of water moving through the drain system, it pushes a wave of high-pressure air in front of it. When this wave moves by an s-trap, the pressure is enough to cause the trap seal to "burp" and admit a small amount of sewer gas past the trap and into the room. (It takes remarkably little pressure to burp past 2" of water. You can try it yourself by taking a brand new p-trap, filling it with water and blowing through the waste end. The slightest breath will do it.)

The solution to this problem - the vented p-trap - allows the high-pressure air to dissipate out the roof instead of through the trap seal. Note that an AAV will not solve this problem. These valves only admit air; they don't vent it.

Proper old s-traps barely merit a mention in my reports. They're certainly not worth fixing.

I read one post about being allowed to put the traps under the floor in Canada, I just wanted to say you not allowed to put them under the floor in Canada it is against the code. Also the first picture is ok and the second one is an s trap and not allowed in Canada either. It is impossible to use proper venting practices with an s trap.

Originally Posted by Bill Brooks

I read one post about being allowed to put the traps under the floor in Canada, I just wanted to say you not allowed to put them under the floor in Canada it is against the code. Also the first picture is ok and the second one is an s trap and not allowed in Canada either. It is impossible to use proper venting practices with an s trap.

Canada is a big country, and much like the US, codes can and do vary from province to province.

I'm not sure which province you're in, but the BCBC, which is the prevailing code in the OP's province does allow a kitchen sink to be trapped below the floor.

Kitchen traps below the floor are also acceptable under the OBC in Ontario as well.

Realistically, since all of the provincial codes are based primarily on the National Plumbing Code of Canada, you'd be hard put to find a province that doesn't allow trapping below the floor for kitchen sinks.