garage floor drains options

[BGTLS]

My concrete guy is going to hopefully pour concrete this week or next and I have a couple of options on floor drains that I would like opinions on. This will be a heated building in northern Wisconsin. It is really a storage building/workshop and will NOT be used for daily driver cars pulling in and out nor will I be washing cars inside the building. The building has 4 stalls and I want to install an individual drain in each of the four stalls and want to keep the floor as flat as possible with only a minor amount of slope around the each parking stall to its drain. I hope to install a lift in on of the bays in the future and do not want to deal with a lot of slope in the floor. I have three options that have been ok'ed by the building inspector.

1. I can tie them into the city sewer system which is already into the building for the bathroom in workshop portion but each drain would need a sediment trap and a P-trap (I am worried about sewer gas when the P-trap water evaporates because I do not anticipate much if any water going down the drains but want them installed now just in case plans ever change)

2. I can drain out the building to daylight which I have the slope out the back of the building to do but have to install sediment trap drains and deal with cold air coming in through the drains in the winter and a possible rodent access point.

3. I can run the drains to sump pit in the corner where I do not need sediment trap drains (the pit serves a the trap) and can install a sump pump to empty the pit if I ever have water that needs to drain from a car or I wash the garage floors. The water can pump out the back of the building through a pvc pipe out the siding in the same area as where the drain to daylight would be if I choose option 2.

What do you guys think?

 

[ford33]

I think none of the above.

You have not provided a need to install the drains. You have listed three options about how to install them and all have issues with maintenance and rodents and local inspections. In winter the drains will freeze.

What purpose does four drains provide when the floor must be level and you do not wash cars in the shop.

Instead of the drains, lay a nice flat level floor and buy a broom to sweep out the shop. Save your money and buy a nicer lift.

 

[rnscustom]

Drains are not allowed here

 

[rossddvm]

If you will ever be pulling a snow covered car into thaw you will want a good drain with a decent slope. Consider doing that with at least one of the bays. I have a 2 car garage with a flat floor and drains and it is amazing how much snow melts of a car and makes a mess of the garage without good drainage. If I park a car in there I have to go out every hour and broom water to the drains to keep it from running to the walls. Makes it damp out there also. I would go with the draining to daylight option. My flat floor has been a thorn in my side for 9 years, I am again looking into a way to "fix" it

 

[Boilerhouse]

I have a 2 car garage, with one drain between the two bays. It drains directly out and behind the garage. It is not quite open to outside, I covered that end with a bit of rock and gravel, and placed a marker on this spot. The drain cover has a sediment trap built into it, and I dump this occasionally. I do not wash cars in the garage, but I get snow melt in the winter, from vehicles and tractor, and that water would otherwise be everywhere and likely damage some wooden cabinets I have. I have never had freezing, and I live in an occasional minus 40 climate.

 

[MagKarl]

I'd also vote for a flat floor, buy a squeegee for the occasional wet mess.

 

[kbs2244]

Number 3

 

[ptgarcia]

If you're going to slope a floor to drains you might as well slope the floor out the doors. If you're dead set on drains, I'd pipe it outside the structure to a dry well or french drain.

 

[Stuart in MN]

Drains are not allowed here

Apparently drains are allowed for the original poster, so that's not much help...


If the inspector has okay'd tying into the sanitary system, my understanding of what many people do for floor drains is to fill the P-trap with mineral oil. It won't evaporate, and any water that goes down the drain will run through the oil and go down the drain while the oil will stay in place. If you run a whole bunch of water down the drain, enough to wash out the mineral oil, it won't hurt anything in the sanitary system.

 

[rburke65]

Drains not allowed in Hawaii either.....therefore...??

 

[joes169]

Apparently drains are allowed for the original poster, so that's not much help...


If the inspector has okay'd tying into the sanitary system, my understanding of what many people do for floor drains is to fill the P-trap with mineral oil. It won't evaporate, and any water that goes down the drain will run through the oil and go down the drain while the oil will stay in place. If you run a whole bunch of water down the drain, enough to wash out the mineral oil, it won't hurt anything in the sanitary system.

I've seen this, and done it myself, many times in the past. Veggie or mineral oil for interior drains that rarely see water (drains in elevator shafts for example) will last for years w/o issue. RV antifreeze in exterior drains that are prone to freezing. I wouldn't put a drain in a garage in a cold winter climate without a p-trap unless you like cool, refreshing breezes in winter.....

 

[BGTLS]

Thanks, for the suggestions everyone and please keep them coming. A very trusted contractor in town echoed the idea of adding p-traps if draining to daylight to avoid the cold air as well. I really do not like the idea of adding p-traps to drains under the concrete. I am really thinking option 3 might be my best option right now but has anyone else ever done this? Thanks again and keep the suggestions coming.

 

[forAK]

Your second option is what I did. 3 drains from 3 bays tie into 1 p-trap under the slab and then goes out. No issues. If you're bringing in vehicles to thaw, the p-trap will stay full.

 

[theoldwizard1]

In many location NONE of those are permitted. You have to check with the local authorities.

 

[Stuart in MN]

Something else you may want to consider is installing a trench drain across the bays, in parallel and next to the doors, attached to a single drain line out. The trench drain will probably cost more, but I think it would make it easier to pour the floor - rather than trying to slope it down in multiple locations to center drains, instead you'd have a mostly level floor with a single slope to the trench drain.

In many location NONE of those are permitted. You have to check with the local authorities.

Yes, but the original poster already said:

I have three options that have been ok'ed by the building inspector.

 

[UNEEKONE]

My local city planners just crushed my dreams by telling me I need to install oil and water separators or interceptors if I plan on doing any mechanic work in the garage I'm looking to build. Those little buggers are crazy expensive...

 

[finn]

My main shop has the oil separator plumbing, as it was originally built to store and maintain logging trucks and equipment. Hasn’t given me any problems, but I am afraid to pull the covers and look what’s underneath.

My other shop has plastic trench drains leading to daylight. The outlet is covered with stones and concrete chips. Never had a rodent problem and there is never water pooling at the discharge.

 

[Captain Spaulding]

I don't really understand the benefit of the drains without a sloped floor. Unless you are hiring a very professional concrete crew, I'm afraid you are going to be disappointed in how the floor turns out. Sloping a slab to a single drain is not easy, especially if you try to minimize the slope. Sloping to 4 drains would be a challenge for most crews in my experience.

 

[Leaflessshadetree]

You could do Option 2 with a "wet" sediment trap. Keep water in it to reduce rodents and cold air. Make it wide enough to fit a square shovel.

Myself I have a good squeegee.

 

[6768rogues]

I have a catch basin type of drain. It is a box with a grate and it connects to a 4" pipe. That pipe exits the building and goes underground for about 75' to a daylight opening. I used solid pipe to 15' away from the building and then corrugated pipe the rest of the way. No cold air or rodents. If a rodent did come in, it would not get through the grate. My lift area is flat.
You need enough slope so they can get the water to drain without ponding.
Traps will dry out and get plugged with sediment. If connected to sanitary and anything happens, they will blame you.
A sediment trap will have to be cleaned. A great job if you happen to have a misbehaving teenager in the house, otherwise it *****.

 

[Randy in Maine]

Here is the "cheat sheet" for MN.....

https://www.pca.state.mn.us/sites/default/files/wq-wwists4-05.pdf

 

[Handyfarmer]

you can pour a flat floor with a tilt in it towards the door, you have a flat floor for many projects that would possibly be built on a floor,

and a slight slope would hardly be noticed, and your water would drain towards the door way,

 

[smalltown]

I have in floor drains to daylight no P trap. Floor is sloped toward the drains no rodents.
I like that fact that any snow on the tractor or cars will melt, and take care of itself.

In my winter climate a sloped floor toward the doors would result in the garage door bottoms freezing to the floor in the winter, and that is a pain.

 

[slimcake]

I have three drains tied together. They exit to "daylight" which I connected to 30 feet of french drain. Dug a trench put some rock in the bottom. Buried the french drain. My concrete guy did a AWESOME job getting each area to flow to the drain. He also left me a nice flat area for my lift in the middle of it all!!