The house we've just moved into has the piping for a full bathroom in the basement floor complete with an ejector pump. My intention is to put a washer\dryer and laundry sink in that area of the basement instead of a bathroom.

There are 4 drain pipes running up from the floor.
Three of the pipes are capped off and the one closest to the ejector pump is tied into the vent line running up from the pump basin and out through the roof.
I figure that I can put a trap and stand pipe on one drain line for the washer and put the sink with a trap on another drain pipe, leaving the others remaining capped.

I understand the rationale behind the arguments against the S-trap, but would those same arguments apply for my layout? The drain line is vented ahead of the other drain pipes.
The distance between the vent line and the closest drain pipe stub in the floor is 2 feet.
The furthest distance between the vent line and the last drain pipe is just over 5 feet.

I’m attaching 2 images. One image showing the hookup with an S-trap and another with a proposed P-trap. It would seem odd to have to run a P-trap with an additional vent line going 24 inches into the other vent line there.

Should I use a P-trap or am I allowed by code to use an S-trap?

The S-trap\P-trap debate is still fresh in my mind after just having sold a house where S-traps were present and a buyer’s inspector dinged me for it.

The house we've just moved into has the piping for a full bathroom in the basement floor complete with an ejector pump. My intention is to put a washer\dryer and laundry sink in that area of the basement instead of a bathroom.

There are 4 drain pipes running up from the floor.
Three of the pipes are capped off and the one closest to the ejector pump is tied into the vent line running up from the pump basin and out thru the roof.
I figure that I can put a trap and stand pipe on one drain line for the washer and put the sink with a trap on another drain pipe, leaving the others remaining capped.

I understand the rationale behind the arguments against the S-trap, but would those same arguments apply for my layout? The drain line is vented ahead of the other drain pipes.
The distance between the vent line and the closest drain pipe stub in the floor is 2 feet.
The furthest distance between the vent line and the last drain pipe is just over 5 feet.

I’m attaching 2 images. One image showing the hookup with an S-trap and another with a proposed P-trap. It would seem odd to have to run a P-trap with an additional vent line going 24 inches into the other vent line there.

Should I use a P-trap or am I allowed by code to use an S-trap?

The S-trap\P-trap debate is still fresh in my mind after just having sold a house where S-traps were present and a buyer’s inspector dinged me for it.
... outlawed by all plumbing code authorities!

The house we've just moved into has the piping for a full bathroom in the basement floor complete with an ejector pump. My intention is to put a washer\dryer and laundry sink in that area of the basement instead of a bathroom.

There are 4 drain pipes running up from the floor.
Three of the pipes are capped off and the one closest to the ejector pump is tied into the vent line running up from the pump basin and out thru the roof.
I figure that I can put a trap and stand pipe on one drain line for the washer and put the sink with a trap on another drain pipe, leaving the others remaining capped.

I understand the rationale behind the arguments against the S-trap, but would those same arguments apply for my layout? The drain line is vented ahead of the other drain pipes.
The distance between the vent line and the closest drain pipe stub in the floor is 2 feet.
The furthest distance between the vent line and the last drain pipe is just over 5 feet.

I’m attaching 2 images. One image showing the hookup with an S-trap and another with a proposed P-trap. It would seem odd to have to run a P-trap with an additional vent line going 24 inches into the other vent line there.

Should I use a P-trap or am I allowed by code to use an S-trap?

The S-trap\P-trap debate is still fresh in my mind after just having sold a house where S-traps were present and a buyer’s inspector dinged me for it.


The house we've just moved into has the piping for a full bathroom in the basement floor complete with an ejector pump. My intention is to put a washer\dryer and laundry sink in that area of the basement instead of a bathroom.

There are 4 drain pipes running up from the floor.
Three of the pipes are capped off and the one closest to the ejector pump is tied into the vent line running up from the pump basin and out thru the roof.
I figure that I can put a trap and stand pipe on one drain line for the washer and put the sink with a trap on another drain pipe, leaving the others remaining capped.

I understand the rationale behind the arguments against the S-trap, but would those same arguments apply for my layout? The drain line is vented ahead of the other drain pipes.
The distance between the vent line and the closest drain pipe stub in the floor is 2 feet.
The furthest distance between the vent line and the last drain pipe is just over 5 feet.

I’m attaching 2 images. One image showing the hookup with an S-trap and another with a proposed P-trap. It would seem odd to have to run a P-trap with an additional vent line going 24 inches into the other vent line there.

Should I use a P-trap or am I allowed by code to use an S-trap?

The S-trap\P-trap debate is still fresh in my mind after just having sold a house where S-traps were present and a buyer’s inspector dinged me for it.


Listen to flickit,

I hate to rain on your parade but the diagram that you call a "P" trap,(#2 gif) is also a "S" trap. Take another look at it. You turned it into a "S" trap when you 45'ed the trap into he drain. If this were my call I'd cap off the first raiser and tie the "P" trap into the raiser closest to the sump with a drainage tee 18" off the floor. Do not install the tee at then same level as the horizontal vent line. With a 2" drain line you may be up to 5 feet from the trap to the vertical vent. Older houses with "S" traps were grandfathered in but today "S" traps are outlawed in both the US and Canada. Questions? Regards, Tom

Thanks guys for help with "the code".

I guess I should have brought an umbrella to the parade.
.. Thought the vented 45 (“T” or is that a “Y”) would've brought under code.
But, if I understand it right, from my drawing in the second pic, the drain would still had siphoned water out of the trap due to the water flowing down the 45?

I took a look under my kitchen sink and saw that a straight T fitting (no curving segments whatsoever) was used to pipe into the vent line there. So, can I infer that replacing the 45’d fitting with a straight T fitting would make it all happy?
(I’m going to make the guess that having the horizontal pipe from the trap end at the 90 of a straight T breaks the vacuum in the drain line.)

Btw.. I see those Y type connections where the pipe from the first raiser is joined to the vent line coming up from the sump basin and larger ones in my waste lines. It appears there are appropriate places for them…and not.

Since this is for the washer drain I’ll put the T fitting low so that there will be room for a stand pipe, that rises from the trap, close to the same height as the washer.

I still have to work in another trap for a tub-sink, so I’ll have to bring a vent line over to it. The last raiser near where the sink is planned for is just about 5’6” from the first raiser closest to the sump basin which is tied into the vent.

Thanks guys for help with "the code".

I guess I should have brought an umbrella to the parade.
..Thought the vented 45 (“T” or is that a “Y”) would've brought under code.
But, if I understand it right, from my drawing in the second pic, the drain would still had siphoned water out of the trap due to the water flowing down the 45?

I took a look under my kitchen sink and saw that a straight T fitting (no curving segments whatsoever) was used to pipe into the vent line there. So, can I infer that replacing the 45’d fitting with a straight T fitting would make it all happy?
(I’m going to make the guess that having the horizontal pipe from the trap end at the 90 of a straight T breaks the vacuum in the drain line.)

Btw..I see those Y type connections where the pipe from the first raiser is joined to the vent line coming up from the sump basin and larger ones in my waste lines. It appears there are appropriate places for them…and not.

Since this is for the washer drain I’ll put the T fitting low so that there will be room for a stand pipe, that rises from the trap, close to the same height as the washer.

I still have to work in another trap for a tub-sink, so I’ll have to bring a vent line over to it. The last raiser near where the sink is planned for is just about 5’6” from the first raiser closest to the sump basin which is tied into the vent.

Use a DWV,(Drainage) tee when you connect. The 45 going into the wye makes it a "S" trap. Since you're putting the washer trap next to the floor why you can't tie the laundry tray trap in 18" off the floor and use the same vant. Regards, Tom