Terry Spragg wrote in message
le.rogers.com..
..
Lew Hodgett wrote:

I can use a bicycle pump or similar to evacuate my holding tank
offshore. I close both air vents, open the sea valve, and pump
up
the holding tank with air. I watch the joker valve for back
leakage
/ wear indications, and now, use a 12 volt tire pump. When the
pressure reaches about a pound, out goes the poo.

Hmmm. Be careful about pressurising HDPE tanks though. Mine
overfilled once, and scum blocked the vent (which had a gauze
cover). Just as the next user was calling out "the head pump is a
bit stiff!" there was a big bang. The tank burst along one seam.
You can imagine the rest.

I no longer have a gauze cover over the vent . . .

JimB
Yacht Rapaz, sadly for sale (no that's not why! It's cos I've
bought a nice Greek house)
http://homepage.ntlworld.com/jim.bae...cification.htm
jim(dot)baerselman(at)ntlworld(dot)com