They used to have a metal plug at the bottom but all the new ones are made of thin plastic where they can't be unscrewed and replaced with a metal plug. Moreover, even with antifreeze and flushing the lines with air, they will freeze and crack in the winter. There is no easy way to remove water. I have now replaced 5 (my van has 2 toilets) of these and will now be forced to replace my toilets with another brand. I'm tired of turning the water back on in the spring and having a massive flood in my RV ruining everything. The only other solution is to remove them during hibernation, but that's already too much, I already have enough worries and projects. I will find the best brand.