Tool
How long the sewer hose needs to be
Measure the path the hose will take, not the straight line through the picnic table. Then give the fitting some slack so it is not holding the hose up.
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Slope is at the target
20 ftThe hose path itself is 12 feet. Add 2 feet of slack and you are buying 2 ten-foot sections. Actual slope is 0.25 in/ft. Target is 0.25 in/ft.
The drop already meets the target. Still support the hose so a wire-reinforced wall cannot sag into a belly.
A 20-foot kit is enough for this path, including slack.
The assumptions, in the open
- Length is the straight-line path along that route, using the horizontal run and the vertical drop as a right triangle. The drop is small, so the hose is only a little longer than the ground distance. Slope is the number that changes the setup.
- Kits are sold as 10-foot sections. A 20-foot kit is two of them. We round the purchase up to the next 10 feet.
- One continuous hose beats two hoses joined with an extra fitting, when the length allows. Every joint is another gasket.
- A support is still required when the slope is already enough, because a wire hose will sag into a belly.
- If the inlet is higher than the outlet, enter a negative drop. The calculator will ask for more lift than the raw height difference.
Park dump stations sometimes sit farther away than a campsite hookup. The national park campground finder notes which parks have a dump, and a few of them tell you to bring a long hose. The hose roundup is the shopping list after you have a number.
Questions worth answering first
Why add slack?
A hose pulled tight turns the bayonet into a lever. That side load is how fittings crack and how gaskets weep. Two feet is the default for the sweep off the bumper and the connection at the inlet. Add more if you have to route around a stabilizer or a picnic table.
Why a quarter inch per foot?
It is the usual minimum slope that keeps wastewater moving in a drain. RV sewer hoses are the same idea in a flimsier pipe. Steeper is fine. Flatter leaves solids in a low spot. The support lift is how many inches to raise the RV end so the run hits that slope.
Does the elbow length count?
The slack covers a normal sweep. If you add a second elbow or a wye, add another foot. The clear elbow on a RhinoFLEX or Dominator kit is bulky. OUTPRIZE's storage tube says that elbow will not fit inside the tube.