Dumb Garage Drain Question

[beartoothweb]

I'm putting in several floor drains, 4 in fact, plus, I'm daylighting my sink as well. I live in the boonies, so I can do that, and I'm careful not to get anything too nasty in there (just car washing, etc.)

The sink will just be used from a gravity fed tank, I'm too far out to do real plumbing lines, and the cold here makes me not want to deal with permanent water. I'm adding a conduit in case I decide to add some later.

At any rate, on to the question...I'm laying down 2" PVC for the drains, I figure that's adequate and will help to limit backflow of cold air into the building when not in use.

I'm laying down about 8" of compressed gravel under the pad. Do I sandwich the drain pipes between layers of gravel, or do I set it on grade and gravel over it? I was concerned that I'd have some sinking under the pipe and make the concrete crack.

Thanks guys!

 

[PurdueSD]

I used floor drains like this on my system. Its drain to daylight also. The traps will evaporate over a couple weeks but a 5 gal bucket can solve that.

 

[Kevin54]

You can put it between gravel or underneath. If underneath, put it on a layer of sand (preferred). Also for a water drain, you only need 1 1/2" pipe. 2" is usually reserved for clothes washers and sinks with garbage disposals

 

[kbs2244]

I would go the other way on pipe size.
4 inch.
On a gravity system you do not want the pipe completly full.
You need air above the water.
If you check your house plumbing you will see that all the horizonals are at least 3 if not 4 inch.
Washers and such are pumped water that is under pressure.

Use sand or pea gravel all around the pipe.
If you are going to air and are worried about wind blowing in put a down facing 90 on the end of the pipe.
Or even a little shed to shield it.

 

[Kevin54]

I would go the other way on pipe size.
4 inch.
On a gravity system you do not want the pipe completly full.
You need air above the water.
If you check your house plumbing you will see that all the horizonals are at least 3 if not 4 inch.
Washers and such are pumped water that is under pressure.

Use sand or pea gravel all around the pipe.
If you are going to air and are worried about wind blowing in put a down facing 90 on the end of the pipe.
Or even a little shed to shield it.

The pipe would not be completely full on a gravity drainage. It would only fill full on a forced drainage (toilet, disposal, washer) or forced dump. On a house the main would be a 4" but all feeds into it are smaller and sized to what kind of drainage it is. Even a bathtub only runs a 2" horizontal to a main due to the multi gallons of water dumping at once. Running a sink or a floor drain to a daylight drain, would take a massive amount of water to fill a 1 1/2" or 2" pipe all at once.

 

[beartoothweb]

The pipe would not be completelt full on a gravity drainage. It would only fill full on a forced drainage (toilet, disposal, washer) or forced dump. On a house the main would be a 4" but all feeds into it are smaller and sized to what kind of drainage it is. Even a bathtub only runs a 2" horizontal to a main due to the multi gallons of water dumping at once. Running a sink or a floor drain to a daylight drain, would take a massive amount of water to fill a 1 1/2" or 2" pipe all at once.

Thanks for that clarification. Also, the drains will only be used for 2 things...1) bucket-based washing in the winter inside, and 2) gravity fed hand washing in the slop sink (very minor amount of water use from an overhead tank).

The only time it would be a HUGE amount of water is if the tank falls off the stand, and in that case...I've got bigger problems.

 

[Mattlt]

Wouldn't the trap on a floor drain freeze up? Wouldn't you need to blow it out or put some anti freeze in it?

Assuming you're not heating your building.

 

[Kevin54]

Wouldn't the trap on a floor drain freeze up? Wouldn't you need to blow it out or put some anti freeze in it?

Assuming you're not heating your building.

You really don't even need a trap due to the fact that the drain is not going into a sewer or septic. A trap is used to prevent sewer gases from backing up through the drain. With a daylight drain all that would be needed is an elbow for the transition. That would eliminate any freezing possibilities.

 

[beartoothweb]

You really don't even need a trap due to the fact that the drain is not going into a sewer or septic. A trap is used to prevent sewer gases from backing up through the drain. With a daylight drain all that would be needed is an elbow for the transition. That would eliminate any freezing possibilities.

That's what I'm planning, just simple elbows and T's to connect everything. I remembered that wind won't actually be an issue since the end pipe will be under a foot of gravel or so.

 

[herb101]

Even if the wind raised an issue, just drop a rubber mat or cap over the drain when not it use. Something heavy, just to prevent too much free air passage. Need to use the sink? - lift the mat and go to it.

 

[beartoothweb]

Let me ask a follow up question:

I currently have 4 floor drains planned for the 40x30 shop, 2 near the doors in 2 bays, and 2 near the back (8' off the wall) of the shop.

I have a lift that's going in, so the intention was to put a drain in front and in back of it, then 2 more for the other bays.

Is this overkill? I'll be using the flat-concrete squeegee method for water management vs. leveling the concrete to run to the drains.

I've attached a pic. I guess what I'm really wondering is if the front 2 drains are needed since most of the water/snow will be near the doors where the vehicles are.

Thoughts?

 

[Dragster Racer]

I can tell you that yes, they do freeze. I thought you wanted the p for keeping cold air out, which it would do. They are a hassle though, and if you can get around it, just use an elbow. Mine froze this winter before putting rv antifreeze in it. That stuff will freeze too, but won't break anything. When I get the shop heated, this won't be a problem.

 

[kbs2244]

Actualy Kevin you are making my point.
Small pipes with lage volumes become, in effect, pressureized.
But, in the end, I will agree with you.
With his small useage and reltivity short run the water will not fill a 2 inch pipe unless he dumps a bucket into it.
That said, if it was mine, I would go with at least 3 inch.

 

[Jay H 237]

On the end that exists at daylight you might want to put a small screen, like hardware cloth or chicken wire, so it will eliminate critters from trying to crawl up the pipe. Don't use a small screen like window since it would clog easily.