Rino.
How to determine the length you need.
No two campsites are ever the same, ever. Every campground you go to will be different. Traveling to a new campground will always have lots of unknowns. And even campsites within the same campground will all be different and have different unknowns.
Assuming your campsite has sewer hook up and you travel a lot, and never know what you are getting into, here's a pretty good rule of thumb.
First, too much is better than not enough. So, if you have extra sewer hose you don't use, it's perfectly OK. Don't be skimpy with sewer hoses, water hoses, or electric extension cords.
Second, always assume the location of the campground sewer location will be about 10 feet behind your camper. Believe me, we've run into a few like this over all the years of RV ownership!
Measure the distance from your sewer drain on the camper to 10 feet behind the end of the camper. If you have more than 1 drain outlet, measure the distance from the once closest to the front to 10 feet behind the camper.
Third, get various lengths of hoses so you can hook together different combinations of length as you need them.
My closest-to-the-front dump valve is about 25 feet from the rear of the trailer. Add another 10 feet, and for almost any campsite I may land on, 35 feet of hose will cover me.
If the dump is forward of the trailer, I'll have sufficient hose. If the dump is off the side, away from the site 15 feet out, I have enough hose.
For my 35 feet requirement, I have one 20 foot hose, and 2 ten foot hoses. But sometimes, I like to connect both outlets together. So, each outlet has 1 ten foot section, connected to a Y with hose that will reach 35 feet. So, that means I carry all the time, a minimum of 55 feet.
55 feet sounds like a lot, but I have, in the past, used all of it.
Fourth, not every campsite if full hook-up. If you camp at an Indiana State Park, chances are pretty good you'll have a site that is electric only. If you want to dump, you either drive your camper to the dump station, or you use a blue tote.
At dump stations, I have found a 10 foot hoses is almost always adequate. But I have on a few occasions had to hook 2 ten foot hoses together, since I have 2 dump outlets on the trailer. If I'm not centered exactly, the 10 foot will not reach one outlet or the other. Rather than jimmying the trailer back and forth, it's just easier to hook up a second hose for the distance.
As stated, I carry a Y adapter for the hoses. I also carry a 3rd valve attachment (Flush King) so I can back-flush the black tank with the grey water, and see what's really coming out of the tanks. I carry a rubber doughnut shoving in the campground drain if the drain is not threaded. I also carry a threaded attachment for the hose end that stick in the campground pipe. Sometimes, with full hook-up sites, the pipe in the ground is broken, or not threaded. The rubber doughnut makes a good seal this way.
I don't have Rino hoses, but I did switch my hoses over time so they all have the Rino type connection, that actually snap and catch and don't slip off. About ever 5 years I'll replace a hose. I replaced 3 of them last year, not because of pin holes, but because the spot where the hose connected to the ring started leaking.
I also keep a 10 foot hose at home at my septic tank opening so I can dump into my blue tote when home. This way, I don't need to drag stuff out of my dump station supplies box.
I keep all my hoses in a plastic WalMart steamer trunk look alike. It's big enough to hold all the hoses, connections, and supplies. The box rides in the back of the pick-up or on my cargo carrier on the back of the trailer bumper, depending upon how much firewood I bring along in the back of the truck.
I suppose the bottom line is, if you travel much and go to new, never been to before campgrounds and campsites, you never know what you are getting until after you get there. It's better to be prepared for the worst case scenario and not need it, than to fall short and have an unhappy camping experience.
Now.... If you are camped seasonally on one spot, you only need enough from your camper drain to the campground drain. Nothing more.