Thanks MK. Yes removed pump and cleaned, also removed cover found inside drum and ensured drain hose is clean. Pump does get hot although problem can happen at first drain after no use for days. Really has me stumped - why it works fine sometimes then doesn't other times. Also forgot to mention - drain hose has been connected to a "grey water" hose to take waste out to garden for years. Have removed extra hose - problem still exists.
Greg
December 2010