Claus

I can\\\'t get my head around this one and i know you would not raise this unless you had a valid point so can you put some more \\\"meat on the bone\\\" please with the explanation.

When water is coming into the tank air must be vented and vice versa on emptying, if the main hatch is open slightly this should suffice unless you are saying that the water level could still be sealing the red/black hatch area whilst the front of the tank say is say trying to empty. If that is correct does this standing vent need to be located in a specific area of the tank.

When you say it must never be operated i take it by that you meen hand primed by vertical movement as per the video on the manafacturers web site but for that to work the far end of the tube must be lower than the pump not sure how you could achieve that.

What i can get my head around is with the tank full and all tank access ports closed which is desirable to stop the water sloshing around in the cockpit and the you want to drain the tank using your bungs whilst sailing the tank needs to be vented.

So in summary

Standard boat with no bungs using forward tank auto bailers to empty on the move does this need your auto vent to overcome vacuum build up. No guidelines documented on procedure so some people leave forward access ports slightly open some i understand leave main red/black open.

Modified boat with drain bungs in rear of tank either self draining or pumped needs automatic air vent somewhere in the tank to prevent vacuum build up when all tank access ports are closed.

I allways look forward to reading your forum notices because confidence is there that you have spent time and effort before posting.