<blockquote><font class="small">In reply to:</font><hr /><p>BTW: the vent is non propulsive i.e. it vents through 2 ports which are opposite each other.<p><hr /></p></p></blockquote><br /><br />Cool! I'd never even thought of that, but it makes perfect sense to do it that way. Silly me, I'd never even thought that the venting could impart thrust if they weren't careful about it. What a simple solution to the problem. <img src="/images/icons/wink.gif" /> I like!<br /><br />That brings up another thought. Does wastewater venting have to be set up the same way, to counteract its own thrust, or is its thrust small enough not to bother? <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>