Question for the Plumbers

[GT2]

I'm building a new home that will have a "conditioned" crawl space.
It will be like a mini basement with a concrete floor.
I want to put in a floor drain with trap ( to exterior dry well ) but I'm not sure how to vent it.
The drain will be roughly in the middle of the floor. I dont really want a vent coming up in the middle of the floor.
Any advise?

 

[Damifino]

I'm building a new home that will have a "conditioned" crawl space.
It will be like a mini basement with a concrete floor.
I want to put in a floor drain with trap ( to exterior dry well ) but I'm not sure how to vent it.
The drain will be roughly in the middle of the floor. I dont really want a vent coming up in the middle of the floor.
Any advise?

Don't know about your state, but here in Fl, you can run 15' from trap to vent. If you have your exterior wall within that range, you could run vent in exterior wall.
Venting of a floor drain and say a sink are totally different, I would run 3" and use a 3" trap, even though you are tyinf into dry well, you will need to pour water in trap to recharge as odors will pass into crawl space or you could use a trap primer and tie into closet sink.

This shoots a small amount of water into trap every time fixture is used, like I said, your codes may vary.

 

[JB4310]

Why would you need a vent or a trap for a floor drain to a dry-well?

I do basement waterproofing, we refer to dry-wells at wet-wells as they can not be relied upon. Not saying yours will not work, but in the area where I service they are not reliable due to soil conditions.

In my area, if that floor of your crawl space was even 1 inch below grade, I would recommend a sub-floor drainage system around the inside perimeter and a discharge to daylight or sump pit and pump discharge. Floor drain could still be installed for plumbing problems etc.
But that's our area, and it may be unnecessary for you.

JB

 

[BeezFun]

I want to put in a floor drain with trap ( to exterior dry well ) but I'm not sure how to vent it.

Don't need to use a vent in the traditional sense if it's not connected to sewage system, because you can't draw sewer gases into the house. With a drywell you typically put a combination vent/overflow on top of the drywell so that if you pump into it and it gets full, the water will flow out the top onto the ground. The vent allows makeup air as the volume of water in the well changes. These things attach to the end of the PVC from your house, and drops down into the well and has a fitting on top that holds a popup cover that also allows drawing in air as water level drops in well. They sell them at Menard's and places like that. If you buy the drywell shell as a kit, the fitting normally comes with it.

 

[JB4310]

If the dry well would allow over flow onto the ground without backing up into the crawl space. That means the surface grade where the drywell was, is below the floor of the crawl space, in which case just have a daylight discharge, no need for a drywell.

Might consider a backflow preventer though, if you don't have the topo for a gravity daylight drain.

JB

 

[Damifino]

Since I'm not familiar with codes in your area as they pertain to what you want to do, as others have said, it will work without a vent.

Since you're building a new home, there would be inspections and the AHJ will make the final call. Might ask when getting your'e permit, unless you are taking a different course with the drain.

 

[JB4310]

Floor drains are huge bone of contention regarding environmental concerns.
Can't have them in shop/garage floors at all with out elaborate separators. Nasty things tend to get poured down floor drains.

Some one mentioned the traps drying out and allowing gasses to bypass, I've heard where floor drains are needed, like commercial kitchens etc. a water service feed line has to be supplied that will keep the trap filled with water utilizing some kind of float mechanism I guess.
Looked online but can't find anything to confirm this.

JB

 

[Damifino]

Floor drains are huge bone of contention regarding environmental concerns.
Can't have them in shop/garage floors at all with out elaborate separators. Nasty things tend to get poured down floor drains.

Some one mentioned the traps drying out and allowing gasses to bypass, I've heard where floor drains are needed, like commercial kitchens etc. a water service feed line has to be supplied that will keep the trap filled with water utilizing some kind of float mechanism I guess.
Looked online but can't find anything to confirm this.

JB

Yes JB, they are called trap primers. they are used in most commercial establishments, and locations where water is not discharging in trap for extended periods of time. as far as food preparation goes, a lot of codes require a backwater valve on the discharge sanitary line.

Here's a couple of the most commonly used around here.

 

[MarkV]

Good information from some knowledgeable people. I am trying to figure why one would put a floor drain in a conditioned crawl space? Do you foresee some type of water problems in your new house? Just can't see why I would do that.

MarkV

 

[GT2]

Thanks for the ideas guys, I'll check with the inspector when I pull the permit.
The reason I want a drain is because of all the water in the house, radiant floor heat, two water heaters, sprinklers. Just cheap insurance in case of a leak.