drainagelaundry
I’m looking into a new construction home that lacks a floor drain in the laundry room. As I’m not a plumber, I’d like to understand how trivial or not trivial it is to add this, in case the builder pushes back on the ask.
It seems like it’s real simple as it’d be a separate drain pipe that, at some point, connects to the rest of the drainage system. Is it that easy or are there complications?
You most likely will overflow the floor drain and damage your surrounding walls/floors.
If it were me, I'd install a new sanitary tee in the main drain, just above the existing sanitary tee. I'd have the standpipe for the washer come down into a P-trap, and connect the other end to the new tee.
However, you'll have to make sure the standpipe is at least 18" above the trap weir. If that height cannot be maintained, you'll have to move some things around.
I'm also not sure if a proper P-trap will fit in the stud bay, so you'll have to measure to verify. The minimum length of a trap arm is two pipe diameters. So if you're using 2" pipe, that's 4" from trap weir to the sanitary tee.
Then I'd have the trap from the washtub, connect to the existing sanitary tee.
Basically, something like this...
Best Answer
You need proper slope on the pipe—depending on the location of the drain and the location of the stack this may be difficult. At least with a crawlspace assuming sewer level is lower than the floor (ceiling assembly of the crawlspace) you should be able to make a giant mess of pipes that just hang and not have to touch framing. A builder will probably have to pull the plumber in to make the change. Even simple changes are going to be relatively expensive. Probably not as much as if you hired a licensed plumber to do it later but I wouldn't expect it to be much less.
The floor where the drain is located also needs to be sloped appropriately for the drain to have the best effect. Unless the floor drain hooks up to a pipe before a trap, it will need its own trap. This trap will be subject to drying out since it won't be in regular use and you'll have to periodically dump water down to prevent sewer gases from coming up unless you have a self priming water valve that occasionally drips water into it.
There is also a critical arm length for the pipe from the trap exit to the vent to prevent siphoning but presumably you'll be in range since the laundry machine also needs to be within this range for its trap.
I went with a flood safe solenoid and a water sensor that turns off the water to my water heater if the sensor detects water on the floor. These exist for laundry machines as well. You can even get a setup that texts that water has been detected and the water to the machine has been shut off. This might be cheaper than the floor drain route—though in principle I like passive insurance. I also go with a washer pan under the washing machine; you could put the sensor in the pan.