How to fit water supply lines in a tight bathroom vanity
Standard plumbing fixtures and rigid supply lines often leave no room for the P-trap or back panels inside modified or non-standard vanities. This forces installers to cut into the cabinet material just to make connections fit without kinking the lines.
What the numbers show
Counted from the threads quoted below. How we count
- People have been saying this in most months since September 2026.
- This comes up 17.0× more often in r/Plumbing than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
How to fit water supply lines in a tight bathroom vanity
- 1Adding a tee with a compression capDid this help you?
- 2Removing material from the back of the vanity to accommodate the bend radiusDid this help you?
- 3Using a flexible plastic tube or flex connectorDid this help you?
- 4Cutting a U-shaped notch or cutout in the bottom shelf of the cabinetDid this help you?
- 5Opening the wall to raise the sanitary tee and waste armDid this help you?
- 6Installing an air admittance valve (AAV) setupDid this help you?
- 7Replacing the vanity with models featuring better drawers and usable storageDid this help you?
- 8Frequently cleaning off the counterDid this help you?
- 9Using handicap accessible sink drain configurations to route pipes back to the wallDid this help you?
- 10Planning to anchor water lines or reconfigure drain trapsDid this help you?
- 11Cutting notches into the vanity drawers to make room for the pipesDid this help you?
- 12Installing an open-back vanity instead of one with drawersDid this help you?
- 13Using a low-profile, space-saving, or adjustable drain kitDid this help you?
- 14Modifying the rough-in plumbing to align differentlyDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Ours looks fine, but the storage is so bad. The plumbing takes up a huge chunk of the cabinet, all the little stuff just kinda gets thrown wherever, and somehow the counter is covered in skincare, toothbrushes, hair stuff etc. basically immediately after I clean it”source ↗
“I am installing this bathroom cabinet but when making it I forgot to take into account the space in the bottom for the P trap.”source ↗
“My wife has crammed them so full that i find them impossible to get anything.”source ↗
“Wife picked out a vanity she liked however I don’t see a simple hookup without modifying the drawers or plumbing.”source ↗
“I have roughly a 5 1/2 inch cavity between underside of countertop and the drawer below. There is roughly a 2” cavity behind the drawers I can use as well, but wondering where I should put the p trap and if it’s too small of a space to make work without modifying the next drawer.”source ↗
“I was looking if there was any way of doing it without cutting but I knew that would be the other option.”source ↗
“If you buy vanities with drawers, just plan on cutting pipe or drawers, I’ve never had one that outright fits without making any changes”source ↗
“Short version: looking for a [3/8" OD compression inlet] to [3/8" OD compression outlet] 90deg elbow fitting - basically the picture above, without the extra outlet on top.”source ↗
“The "vanity" I'm trying to put in is not actually designed to be a vanity, and I'm trying to minimize the amount of material I have to remove from the back of it.”source ↗
Where this came up
People with this problem also raised
- 9No room to fit a plumbing vent in tight spaces
- 2Will twisting a trap cause toilet water to clog my shower?
- 3How to install a vanity over floor pipes in a tight space
- 3How to loosen bathroom water lines in extremely tight spaces
- 6How to figure out a master bathroom layout with tight space
- 5Double vanity plumbing slope and drainage issues