How to figure out correct plumbing and venting requirements for a remodel
Conflicting advice from professionals and contradictory local codes make it nearly impossible to find a definitive answer for DIY plumbing and venting layouts. Without clear guidance, homeowners are left guessing on critical setups like washer drains and pressure relief pipes, risking major code violations or abandoning projects altogether.
What the numbers show
Counted from the threads quoted below. How we count
- This comes up 17.4× 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 figure out correct plumbing and venting requirements for a remodel
- 1Hiring professional plumbersDid this help you?
- 2Searching online forums, the web, and asking AI for homeworkDid this help you?
- 3Trying to do the plumbing work yourself without a permitDid this help you?
- 4calling installers to have them route it to the nearest floor drainDid this help you?
- 5routing the pipe to the exterior or a drip panDid this help you?
- 6Asking online forums for feedback on rough-in photosDid this help you?
- 7Relying on local building inspectorsDid this help you?
- 8Hiring professional plumbers or consulting plumbing codesDid this help you?
- 9looking up data tables and doing independent searchesDid this help you?
- 10asking for explanations on online forumsDid 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.
“That shower is not vented where I am from. Flushing the toilet could possibly siphon the shower trap.”source ↗
“DIY’ing basement bathroom Just finished roughing in shower drain where toilet was and shifting everything down. Ready for inspection?”source ↗
“I have had two plumbers come by, and they had different ideas about how to plumb this. One giving me an absurd estimate (almost 5 figures), and the other one ghosting me. I have looked all over the web, asked AI, been on the Terry Love forums, searched through reddit, and I cannot find a definitive answer.”source ↗
“so homeowners responsibility, not the company that installed it? guessing it depends on state codes”source ↗
“The shower has no trap and no vent...not a plumber, but that looks off...”source ↗
““All horizontal branches are greater than one branch interval apart” What exactly does that mean and how is the answer 3”?”source ↗
“Redoing my laundry room (which includes a toilet), and the current plumbing is no bueno. (1.5” drain on the washer, no venting pretty much anywhere, etc.)”source ↗
“Pressure relief pipe pointed to the floor. no drain in the immediate area. the closest one is 10+ feet away under the laundry sink. we're in Minnesota. doesn't seem right to me”source ↗
“So, I’m old. Way back when a pressure relief valve had to be installed on the hot water line coming from the tank. Is this still the rule? I’m changing the hot water heater and I don’t see one installed but the tank has one on it.”source ↗
“I don’t want to build a bomb… please help!”source ↗
Where this came up
People with this problem also raised
- 14Where do I run the vent for a washer installation?
- 2How to route a plumbing vent offset around obstacles
- 2Vertical exhaust pipe clearance near side entrances and air returns
- 6How do I know which plumbing parts to buy for a DIY repair?
- 29How to figure out confusing plumbing and water flow directions
- 3Will half-inch pipes cause pressure drops in a second bathroom?