The weather forecast for the Daventry area where Harnser is moored indicated that Friday night could well have temperatures in the region of -6 and day time temperatures not getting above Zero. I use Metcheck to keep an eye on the weather for the area I am cruising in. From this on Thursday we decided that we would go to the boat Friday and drain the fresh water system, a job I normally do after Christmas. The weather station on the boat indicated the the lowest outside temperature had been -3 and inside the boat -1.
It is relatively easy to drain our system, I just isolate the main tank, remove the cover from the inline strainer to let air in and start the pump by opening a tap. This allows the pump to pressurise the system with air, I then open the cold taps to blow as much water out as possible before switching the pump off. I then open the hot taps and a valve between the calorifier fill connection and the bath drain. This allows water to drain from the calorifier into the bath and air to enter via the open hot water taps to prevent a vacuum being formed inside the calorifier and causing an implosion. To speed things up I can put the waste plug in the bath and start the bath emptying pump,this then sucks water out of the system and pump it overboard.
Once it is all complete I replace the strainer cover,close the valve between calorifier and the bath waste, so when I return to the boat I just have to open the isolation valve on the tank and switch on the pump to refill the system, as water starts to come out of the taps I just go round closing them in turn, wait for the pressure to build up and the pump to stop to ensure there are no leaks.
Whilst we were there we also ran the engine for a bit taking the boat down to the top lock and back, this not only charged the batteries a bit but saved us carrying the nonperishable things we had taken to the boat over the lock and down to the moorings.