Can a Toilet Drain Drop Straight Down?

Vertical Drop

When the toilet drain reaches a vertical wall, it drops straight down between wall studs. Although this is a vertical drop, don't use standard 90-degree plumbing elbows, called "hard 90s," to connect the pipes. The sharp corners on these elbow fittings can increase the risk of clogs.

Does a toilet drain have to be straight?

A toilet drain can have bends. It's recommended to avoid having a 90-degree bend as this will lead to blockages and unwanted damage. Instead, it's best to restrict the bend to 45-degrees and then place a straight pipe before adding another 45-degree bend.

Can a toilet drain run horizontal?

Only 3 total water closets are permitted to discharge into any 3 inch horizontal drain in the UPC. The IPC does not have this limitation. It's 4 inches on the inlet of the fitting and 3 inches on the outlet. The plumbing code never allows a drain to be reduced in size in the direction of flow.