Seemed like the logical place to post this, knowing that alot of you are pretty sharp on these things...

I'm wondering if anyone can tell me what size pipe would be required to carry a minimum of 17 gallon/minute of waste water...or where I might be able to find that kind of info. I'm trying to work out plans for our laundry room and the biggest hurdle at this point is the drain line for the washing machine.

The current setup is that the washer drains into a 20 gallon (I think) plastic utility tub which then drains into a floor drain through a gate valve, which is used to "throttle" the rate of flow out of the tub. Not the setup I would like to have.

Any input appreciated!!

 

Our washer has its own 1" hose that goes into a 2" PVC drain.

 

Most setups that I've seen (including mine) have the drain hose hooked over the edge of a laundry sink. I think our sink has a 2 inch drain. The water does rise in the sink, but it never overflows -- of course you have to keep the drain clear.

Does your washer really do 17gpm? Seems like a lot.

 

That's how it's been in every apartment/house I've ever lived in. I'd say a 2" pipe should be more than plenty.

 

For a first approximation you can use a drain pipe the same size as the discharge hose from the washing machine [it does flow 17 gpm, no?]. Anything larger would also work.

There isn't an easy correlation between just pipe size & flow; pressure needs to enter the equation as well. Higher pressure thru the same opening will flow more liquid....

 

The 17gpm figure comes from the manual for the washer, referencing the use of a drain line that will handle that amount at a minimum. That's a good point that zooom made concerning the pressure relating to gpm flow, and I realize that restrictions in the line (elbows and such) will also play a role. I may have to do some experimenting, but I know the pipe of the current floor drain would have to be extended above the floor, and a P-trap and vent would need to be installed as well. Hmmm...looks like a trip to Home Depot may be in the future.

I'm still open to any other thoughts on the subject!!
Thanks to all!

 

You can get 17 gpm out of 1/2" pipe. There are a lot of factors to consider. The manual says it puts out 17 gpm, but your washer (depending on type) probably doesnt use that much. Its what the discharge pump is capable of doing. I know of a well pump that can do about 80 gpm out of a 2" pipe. You will be fine with a minimum of 1 1/2" pvc pipe.

 

inch and one-half pipe will work fine. That's what the plumbing code calls for. However, you need a 3' lenght of 2" pipe on top of the trap to accept the soap suds.

 

In N.C. the drain has to be 2". Also if you're tying it into a line with a floor drain, toilet etc. make sure you put the connection downstream from that fixture's vent. Also a good Idea and enforced in some areas is to have it connected 5' downstream of another fixture due to the siphoning effect from the washer pump. If not hooked correctly the washer can siphon other fixture's traps dry resulting sewer gas in the dwelling.

 

My set up in the laundry room is just a 2" pvc pipe coming out of the wall. The discharge hose from the washing machine just goes into the pipe. I've never had a problem.

 

So in theory the existing drain pipe in the floor (which measures 2") should be adequate as a drain line for the washing machine.

I've determined that this line, which is in a corner about a foot from the exterior wall, goes downwards just enough to clear the concrete slab floor and then makes a 90* bend outwards from the house and heads off in the general direction of the main septic line somewhere under my driveway. There are no other fixtures on this line, nor is there a vent anywhere.

My hope is to also install a new utility sink that would also utilize the same drain line. As I understand it, I would need to install P-traps for the sink and the washer, and will need a vent line for each one as well. My thinking is that they would each be placed (basically) on opposite walls of the room with the existing drain being along the wall between them. This may take some doing, but with the info I'm getting from all of you I'm thinking this may be workable.

Thanks! And if anyone has any other thoughts on the subject I'm all ears!

 

Just a couple more notes that may help

*Do not lay DWV tee's on their side's or back (vertical only)
*Minimum 2" DWV piping under a concrete slab