[coach42]

Does a vent on a floor drain go before or after a p-trap?

[speedball1]

does a vent on a floor drain go before or after a p-trap?

Somebody gave you bad advice. Floor drains come with a built in trap and in my code area is the only fixture the doesn't require a vent./ However, your code may require a trap primer. Good luck, Tom

[massplumber2008]

Depending on the application, vents are required on floor drains in my area. You install the vent before the trap (see drawing)... usually within 3 feet of the trap. A trap primer is also required in most cases.

Exactly what is the application you are installing this for?

Let us know more, OK?

Mark

[speedball1]

So, we have two different answers. To see which one fits your case contact your local Building Department. Good luck, Tom