Plumbing question: Gray water drainage: need P traps?

[brnctt]

Hi everyone. We are about to have a slab poured for our remote workshop (no house on the plot), and the shop will have a sink and shower. The toilet will be incinerating so we don't need a real septic system. The sink and shower will drain to a gray water pit/field away from the building. I am thinking 20ft of solid 4" to get it away from the foundation, then 30ft of perforated drainage pipe surrounded in gravel, ending in a big gravel pit for overflow. Just the 4" pipe itself, if it ever fills completely up, can hold 40 gallons, so I think this will be more than adequate. We're far away from any kind of natural water and wells in our area are more than 1000ft down, so contamination will never come into play.

The shower won't get much use, and the building will be uninsulated. I'm wondering if P traps need to be installed, on either the sink or under the shower. P traps are only to block sewer gas, right? I'm thinking it would just be something to freeze and break pipes in the winter, if used at that time.

We have no inspections/permits so no worries there, but I want to do it right.

 

[sjvicker]

I'd still plan for a P trap just to make sure nothing comes crawling back up

 

[wssix99]

I'd still plan for a P trap just to make sure nothing comes crawling back up

Unless one wants to roll the dice and see if a mouse, snake, or other animal would pop its head up when you turn on the shower!

 

[southalabama]

I’ve had a snake come up through a p trap.

But

I’d put one in.

 

[lzenglish]

YES on P Trap, 100 Percent, (imo) !

LZ

 

[cgrutt]

Not sure if concern is p-trap vs say, s-trap or p-trap vs no trap. Only argument I can think of not to have any trap would be concern over freezing etc in a remote cabin. IMO you should have some sort of trap preferably at each drain to keep critters and more importantly vapors out of your cabin. Ptrap is better than s-trap as the trap can siphon off and empty with the latter style.

 

[HoosierMark]

If it were me, I would set everything up suitable for using a septic tank. Put a drain in for a toilet and just ignore it. The cost is minimal and you just never know what might happen in the future. Set the incinerating toilet right on top of it. You can even just leave the flange off and cover with tape. Then pour an inch of concrete over it. Plumb it to the outside of the building, cap it off and forget it. That way if you ever need it, you don‘t need to cut the concrete just break the concrete in that area.
But to answer your question, yes put a trap in. Or maybe a backflow valve to prevent unwanted visitors. If worried about freezing put it outside in a pit for access but protected from freezing.

 

[The Cobbler]

P trap? yes... to keep vermin from entering .

 

[Zeke]

Next question: what about vents?

 

[brnctt]

So no one is worried about water freezing in the P traps? This is an uninsulated metal building...

 

[Rst277]

"But to answer your question, yes put a trap in. Or maybe a backflow valve to prevent unwanted visitors. If worried about freezing put it outside in a pit for access but protected from freezing."

 

[The Cobbler]

the plot thickens . I guess you did mention that in the original post .
yes, you should have P traps, and yes they will be prone to freeze.
does the toilet have a trap with water? how will you handle that ?
and what are your plans to keep the waterlines from freezing?

 

[alwaysFlOoReD]

Use RV antifreeze in the traps.

 

[brnctt]

the plot thickens . I guess you did mention that in the original post .
yes, you should have P traps, and yes they will be prone to freeze.
does the toilet have a trap with water? how will you handle that ?
and what are your plans to keep the waterlines from freezing?

The toilet will be electric incinerating. Waterlines will be on a shutoff/drain at the entrance to the building that I will release before freezes (or just for winter in general).

Btw the end of the drain pipe will be probably 2ft underground in a buried gravel pit. Not sure what kind of critters could come up… ants I suppose?

Do you think the shower P trap, being in the slab and under the fiberglass shower pan, would be regulated in temperature enough to not freeze? Does a slab generally regulate temperature better than open air?

 

[bb29510]

techicaly if its not going to a tank, then there no sewer gas so no, but if its open pipe into a dicth, I would want one to keep the bugs out

 

[coldh2o]

If you're shutting the water off for the winter, just put antifreeze in the trap.

 

[brnctt]

Thanks guys, I was unfamiliar with RV antifreeze. Didn't want to pour "real" antifreeze in my grey well.

On a side note though, I think I'm going to forego the shower. Will hose down outside if I get really dirty. My concern is plugging up my simple grey well with clippings and dirt over time (which is the only time I'd be taking a shower, when really dirty).

 

[Jim greengo]

At some point the water sitting in that barrel will still start to stink,I'd use traps.

 

[Jackfre]

The trap is for odor control. You can expect the downstream side to develop an odor.

 

[mreisner]

Soap, body oils and soils will smell as it's always going to be damp down in there where drain ends. A trap is simple cheap insurance to keep the odors out. Clippings Etc will break down Underground. A gallon of 50 below RV antifreeze will last you a long time when you're done taking a shower just pour one cup full down there before you leave the place and it will never freeze. I would keep the shower it sure would be nice to have. $5 P-trap and a $4 gallon of marine antifreeze is cheap. The first time you wash off in that shower or even need to just take her quit shower to cool off it will be priceless.

 

[bb29510]

rubbing alchol will keep it from freezing

 

[Dig Doug]

The trap is odor control

use a trap!
a typical toilet has a trap built into it / an RV toilet does not have Tarp built into it and uses water to seal the toilet from the black tank

a trap has nothing to do with bugs snakes etc. is a block of water to block odors and forces gasses up the vent & thru the roof

gray waste water typically smells worse than black water

Black typically uses a solution to break down solids into a liquid in order to leach out

gray is already a liquid and will smell if it gets stored in a tank like situation, if it gets dumped directly with out a tank it won’t smell

 

[Monza Harry]

The trap is odor control

use a trap!
a typical toilet has a trap built into it / an RV toilet does not have Tarp built into it and uses water to seal the toilet from the black tank

a trap has nothing to do with bugs snakes etc. is a block of water to block odors and forces gasses up the vent & thru the roof

gray waste water typically smells worse than black water

Black typically uses a solution to break down solids into a liquid in order to leach out

gray is already a liquid and will smell if it gets stored in a tank like situation, if it gets dumped directly with out a tank it won’t smell

Dig Doug while that is its primary function by design it offers the additional function that most small vermin/snakes/and insects will resist swimming to get to an unknown area. No not all as some snakes are quite happily amphibious, and therefore it will not help with those, but a better knowledge of the actual location is needed to say for sure! Vermin will also resist the water in the feezing/severe cold and would likely only be chasing heat/shelter. Other than that I think the rest of the comments are pretty spot on! OP also consider your drainage and plumbing layout outdoors carefully as you would benefit in winter to limit standing water in the drainage pipe. Harry