Thread: Sink trap in the crawl

This new construction 2-piece bathroom had the ubiquitous Glass Bowl sink, that wasn't draining very good. Probably the trap's full of drywall dust, I thought. Oh looky, no trap.
The water eventually broke thru and the sink started draining fast like it should. I guess almost a 5 foot head of water helps to flush the drain? []

Should this crawlspace trap have a cleanout, or a removable section? Yes, it should. Does your code require it?


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My recollection is that, at here in the States, the maximum vertical height allowed between the drain inlet and then the trap weir is 24" ... and that looks higher than 24" above the trap weir.

I have a problem with the way the trap drain line connects with the larger drain line.
Goes uphill.

I have a problem of the lack of a proper vent.

Originally Posted by Ron Hasil

I have a problem of the lack of a proper vent.

and support.

Originally Posted by Ron Hasil

I have a problem of the lack of a proper vent.

Originally Posted by Billy Stephens

and support.

I think he is trying for a 'wet vent' arrangement there.

There are three straps holding it. How many do you need?

I'm not defending this arrangement. It is unconventional and the odd angle at the T means the trap arm is always wet.

Would not work here, as you are only allowed a 15" vertical drop on the trap.

Is there anything upstream, as venting could be an issue if there is?

Originally Posted by Mike Kleisch

Would not work here, as you are only allowed a 15" vertical drop on the trap.

Is there anything upstream, as venting could be an issue if there is?

AFAIK, there is no other plumbing in that corner of the shack. So I'm of the opinion that the trap is vented by the drain pipe. I'm still trying to decipher how this passed the judgement of the building official, assuming he opens cabinet doors.

Originally Posted by John Kogel

I think he is trying for a 'wet vent' arrangement there.

There are three straps holding it. How many do you need?

I'm not defending this arrangement. It is unconventional and the odd angle at the T means the trap arm is always wet.

There is only one strap holding the trap line connecting to the drain.

Originally Posted by John Kogel

There are three straps holding it. How many do you need?

Needs to be supported and secured maximum 4 foot spacing.

Metal straps and PVC is a bad idea. They make plastic anchors and securing straps for PVC pipe.

Originally Posted by Ron Hasil

Metal straps and PVC is a bad idea. They make plastic anchors and securing straps for PVC pipe.

What we have here is ABS, and once in a while a bit of white PVC. So this is ABS pipe. The metal strap has been used like this for decades and causes no ill effects that I know of.

This sink has been plumbed as if it is in an island. In my area, BC, a trap below the floor is allowed on an island sink, but the max length of the drain before the trap is 47" (1.2 Meters). This one is longer than that by a half a foot or so. The trap section is removable for cleaning, as required.

I figured someone will point out the fact the picture is ABS not PVC. Let me rephrase it then, metal straps on plastic pipes is a bad idea. As the pipes move (and they do move be it from expanding and contraction, and vibration from water flowing through the pipe) the metal strap will cut into the plastic pipe.

The Illinois code doesn't say not to use metal but does talk about not using a support that will distort, abrade, or cut the piping.

f) Plastic Pipe. Hangers and straps shall not compress, distort, cut or abrade the piping and shall allow free movement of the pipe. Wire pipe hooks shall not be used to support plastic pipe. Restraining joints and expansion joints shall be installed as required. All horizontal piping shall be supported at intervals of not more than 4 feet, and at ends of branches, and at changes of direction or elevation. Trap arms in excess of 3 feet shall be supported as close as possible to the trap.

and here is the bit on traps.

a) Fixture Traps. All directly connected plumbing fixtures, except those having integral traps, shall be separately trapped by a water-seal trap, placed as close to the fixture outlet as possible. A kitchen sink with up to 3 basins may be installed on one trap if one compartment is not more than 6 inches deeper than the other and the waste outlets are not more than 30 inches apart. (See Appendix D: Illustration A.)

b) Distance of Trap to Fixture. The developed length from the fixture outlet to the trap weir shall not exceed 24 inches, except when an interceptor is used as a trap, it shall be located as close as possible to the fixture. The maximum developed length from the fixture outlet to the inlet of the interceptor shall not exceed 5 feet. (See Appendix D: Illustration B.) The standpipe inlet for an automatic clothes washer shall not exceed 48 inches above the weir of a trap.

c) Trap Size. The size of trap for a fixture shall comply with Appendix A: Table E for minimum size of traps. No trap shall be larger than the fixture drain to which it is connected or the drainage pipe into which it discharges.

The Tee Wye is in the wrong position, this makes the water have to flow uphill before it can get into the main line. the Tee Wye should have been inverted and a 45 degree or 22.5 degree street elbow used to tie it in. water dropping can be in a 90 degree elbow down but to change to a horizontal flow it must bee a sweep 90.

By the way, Is that PEX pipe or polybutylene for the supply line. it has copper fittings though and not the plastic fittings.

Originally Posted by Ron Hasil

Metal straps and PVC is a bad idea. They make plastic anchors and securing straps for PVC pipe.

Its ABS not PVC

Any water coming down the line to the sink drain is going to go right up the drain to the trap. The drain line is ABS but the water supply line looks like polybutylene.

Originally Posted by Brian Tilton

Any water coming down the line to the sink drain is going to go right up the drain to the trap. The drain line is ABS but the water supply line looks like polybutylene.

..........supply looks like Pex.........Greg

Installer must have gotten paid by the fitting.

Another problem that you will encounter with the trap being too far down to meet code would be the noise. The water dropping that distance and hitting the water of the trap will create considerable noise. When you guys run water to check out the drainage, listen for the abnormal noise of draining water. It is almost always a ‘dead giveaway’ that the trap is too far from the bottom of sink basin.

Originally Posted by Brian Tilton

The Tee Wye is in the wrong position, this makes the water have to flow uphill before it can get into the main line. the Tee Wye should have been inverted and a 45 degree or 22.5 degree street elbow used to tie it in. water dropping can be in a 90 degree elbow down but to change to a horizontal flow it must be a sweep 90.

Brian, you are correct. The wye went in upside down, which forced the trap arm lower, instead of at the optimum level.

The water supply piping is white PEX. We haven't used PolyB for about 20 years. Yes, Doofus could have done a better job there as well.