<html><head></head><body><div class="yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div dir="ltr" data-setdir="false">Hi All, I am looking for a safety back up on my solenoid vent valve. I envision an upside down foot valve. I want a device that blocks the air flow from the MBT once submerged. This is in case the solenoid valve gets debris in the seat and fails to seat. I only need one auto blocker because I have two MBT's. I can make buoyancy adjustments with the second tank. A float that closes a valve sort of thing</div><div dir="ltr" data-setdir="false">Hank</div></div></body></html>