I finally fixed the water tank leak
Six months of chasing a slow drip under Doreen's passenger-side bulkhead. Turned out to be something dumb.
I have a four-hundred-gallon polyethylene tank bolted to the floor of the van. It feeds a pressure washer and a pure-water rinse system, and every morning I fill it from a hose at home. For the last six months, I'd come back to the van after a job and find a puddle underneath the passenger side that I couldn't explain.
I checked every fitting three times. Replaced the two most suspicious o-rings. Re-taped the threaded inlet. Inspected the tank itself for a hairline crack, with a flashlight, on my back, in the middle of August. No crack. Puddle kept appearing.
The fix
It was the overflow vent. There's a small half-inch vent on top of the tank that lets air in as water pumps out. On my van, the vent hose had worked its way loose from its clip over time and was now hanging low enough that when the tank was completely full and I drove over a bump, water would slosh out of the vent, run down the hose, and puddle under the bulkhead.
I'd been filling the tank completely full every morning because that's what you do. The fix was: don't fill it completely full. Leave an inch of air. And while I was at it, re-clip the vent hose high against the ceiling where it belonged.
Six months. Two o-rings. One roll of plumber's tape. And the actual problem was that I'd been overfilling the tank and a hose clip had popped loose.
Why I'm writing this down
Because I know another mobile detailer or landscaper or pressure-washing contractor is going to hit this exact problem and waste a weekend on it. If you're one of them: check the vent hose first. Always check the vent hose first.
Also, Doreen is sixteen years old and still earning her keep. Respect to Doreen.
— Marco