As bikendan said, they are low water point drains. Pull up on them, they only go about an 1/2 ", and open both your cold and hot water faucet to allow air in so water will drain. If there is enough length on the fittings on the under side of the camper, add a small piece of tubing to keep any water from coming in contact with the flooring and then caulk around where they come thru they floor. On my A128S, I had enough extra length on the fittings to add tubing, you will need to check if this is something you care to do. One other thing, just because they are low point water drains, all the water may not drain out. You could have a water line that has a high point caused for whatever reason during building of the camper. Hope this helps you. Good luck.
2016 Forest River Surveyor 201RBS
2014 Chevy Silverado 1500 4.3L