I would buy two 10-ft hoses. Get good supple ones. The cheap hoses get brittle too fast and crack. Also get caps for the hose ends to reduce messes and smells.
As @Binghi said, two 10 ft hoses are a good choice. You'll also need an elbow for the connection at the campsite. Either of these kits contain the key pieces. There are several other similar choices.
Might want to consider getting a dedicated water hose for the black tank flush connection. It probably wouldn't seem too obvious until you use a dump station.
20 feet of hose seems like about 10 feet too much. In over 10 years, I have never needed more than one 10 foot section of hose. There were a few times when I needed to use nearly every inch, and there were a few times when I had to jockey around a bit to get close enough, but I have never encountered a situation where 10 feet did not suffice.
I have 15 feet which has been plenty. If you are at camping sites with a sewer sump provided you should usually be able to position the camper within that distance
Susan & Bill, Yarmouth, Maine 2024 T@B 400 Boondock Black Canyon 2024 Kia EV9
A few years ago I purchased a Rhino waste tank that I use at home when there isn't a convenient dump stop on the way home. It came with a three foot sewer hose. I travel with that and a 10' hose. Both fit in the storage tube below our T@B. With some dump stations the short hose works better than having to work with clumsy excess length. Other times I may have to connect the two together to reach the opening. The majority of the time the ten foot hose alone works fine.
Stockton, New Jersey 2020 nuCamp T@B 320S * Jeep Wrangler 60,865 camping miles through the end of 2025
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You will need a clear, 90 degree bend. Without the clear section, you won't know when it's done.
"Just Enough"
2024 T@B 400 Boondock Black Canyon
2024 Kia EV9
Ken / 2023 Tab 400 “La Bolita” (31,000+ miles) / 2024 Toyota Sequoia
2020 nuCamp T@B 320S * Jeep Wrangler
60,865 camping miles through the end of 2025