I'm installing a basement floor drain with a p-trap and plan to run a drain pipe 36 inches underneath footer and connect to an existing drainage system. The existing system starts as a footer french drain that originates inside my crawl space with about 40 feet of perforated pipe covered with gravel and happens to be connected to solid pvc where I want to connect my proposed floor drain. At this point, the existing system runs 90 feet of solid pipe to daylight. I understand a p-trap should have a vent. But since the pipe I'm connecting to is essentially vented via the gravel in the crawl space, do I really need to add a vent?

In my area, you would have to have a vent on that floor drain. You may also require a primer trap for that drain.

I am not sure I would recommend connecting floor drain into de-watering system. If you absolutely have to, than I suggest you at least install "check valve" on that drain to prevent possible water back up into your basement during rainy season.

Any way you can connect that floor drain into existing house sewer / drain pipe ? What is the elevation difference between the basement floor and that 4" french drain ?

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Milo

Thanks Milo,

The check valve is a good idea. My sewer line is 6 feet above basement floor level so I'd need a sump pump to use sewer.

The existing french drainage system from crawl space becomes schedule 40 solid pvc when it exits home. It travels 20 feet sloping downward before point where I wish to connect floor drain. It is 24 inches below basement floor level so I have plenty of drop between floor drain and existing drain.

Sounds like a good plan. Don't forget to put primer trap and primer feed line, connected to that basement drain. Otherwise, trap will dry out and you will have smell entering the room.

Good luck with your project !

Milo

Sounds like a good plan. Don't forget to put primer trap and primer feed line, connected to that basement drain. Otherwise, trap will dry out and you will have smell entering the room.

Good luck with your project !

Milo


Would the primer trap be necessary when using a check valve and considering it drains to daylight instead of sewer?

In my house, I would put one in. It is a combination of two things: because the check valves do not seal well until they are fully "closed" by backing up water. And also, traps will dry out as floor drains are not used too often.

Thanks for your helpful advice Milo.