Why cant you use rechargable batteries - this would be cheaper in the long run?

A. there are 2 main reasons. 1. Not many people realise that rechargable batteries are not the same voltage as normal zinc/carbon batteries (or other non rechargable types). Normal batteries are 1.5v but rechargeable batteries are only 1.2v. So your timer, needing 3 volts to work now only has 2.4 volts before you start. 2. Normal batteries dishcharge gradually and fairly consistently over time. This is picked up easliy by the timers low battery function and so the timer is prevented from opening if it cannot shut. Rechargeables give full or nearly full voltage until they are nearly out of power then the power suddenly runs out. This cannot re detected by the timers low batt function. The result is that the may havev enough power to open but not close again and so you may waste water.  more