Our caravan will soon be 10 years old. In the autumn of 2022 I opened all 6 (six!) drain valves in good time before the frost like every year. Dss goes quite simply because “only” the brown lever has to be placed vertically upwards. The valve is opened about 3mm. At the start of operation in 2023 I had to find that the Truma thermal bath has burst and the water is distributed. I found that the valve is fixed in the guide and only the lever (plastic) bends down. So, of course, the drain valve does not work. The force to set up the lever is the same as with an intact valve. So, look more closely at the next time if the valve really opens. With me it was that of the 6 valves, 4 defects and the 2 valves are the discharge valve. sadly have sat in the hot water line. Greeting Volker p.s. in the www. can already find other reports.