Back water valve with drain and p trap install.
Question to be answered, which order of components is correct?
Back story, installing a back water valve in my basement drain because water backs up with hard rains and the laundry machine drain cycle overloads it. Otherwise, never backs up with showers, dishwasher or kitchen drains etc. even when running all of those at the same time to test it.
I got One that opens at the top and you can clear out the line easily and clean the flap. The basement drain has a P trap so I’m going to replace it.
Picture one, conceptually as I understand it, water will be able to move down the drain and open up the flap to move forward but water won’t ever back flow to refill the P trap. This is my only concern but I guess as every once in a while I’d have to just pour a little water down the drain to refill the P trap.
Picture two I don’t have the second 90* angle because I thought of this design after the fact. This puts the P trap direct to connect to the cast iron pipe and then the back water valve and then the drain behind it. This would let the P trap refill any time the water backs up but it would make more bends in the system if needing to snake the drain ever. I think I prefer this design over the first one, my only concern is the wavy aspect of the P trap. It’s hard to explain but this design also allows me to adjust the height of where the back water valve sits on the floor.
Another small general question. Is it recommended you use rubber couplings for underneath concrete because they are more adjustable if drains are not perfectly flat initially? I know it’s required for the connection to the cast iron pipe but it seems nice to be able to put some stuff together and move it around a bit rather than weld it and not be able to adjust it slightly before replacing the concrete.
Thanks!!!!!!