Homemade releaser problems

[Wanabe1972]

I have constructed a releaser useing an old tank from a pool pump. I have a flapper valve in the bottom for sap release and a homemade valve on the top that is attached to a SS float inside the tank. The problem is I cant seem to break the vacuum to allow the releaser to release. The valve on top is just a disc of stiff rubber that sits on top of a pipe. It will fill the releaser up untill the float is completely submerged but not release. If I just give it a little pull it releases and does as it should. The float is 6.5 inches across and 10 inches deep but does not seem to have enough lifting power. This is set up like a hobby style and does not cut the vacuum off when it dumps it just lets the atmosphere in and sap out. Any suggestions how to fix this would be appreciated. By the way Im only running 6 inches of vacuum off a shop vac as my pump is not set up yet. Im sure this problem is only going to get worse with 20 inches on the real pump.

[Dennis H.]

If I understand correctly the float rod is directly connected to the flapper vlave at the top and when the float rises it the rod will force the flapper open?

How big around is the flapper? The larger the dia the more force it will take to open it. If it is just for vac then I would reduce the size down to something like 3/4 or even 1/2/ but not sure the size you made it.

The other thing you could do is somehow make a lever linkage that the rod uses to open the flapper, mechanical advantage thing.

How heavy is the float? did you add any weight to it? Maybe you would need to remove some if you did.

Pics would be helpful also.

[jasonl6]

You need more surface area to for the fluid to push up against. Trying making a square out of 2" or 3" pvc.

[Wanabe1972]

Thanks for the input. The hole on the top is 2 inch and the float is made out of 16 guage SS so it weighs about 5 pounds. I can reduce the size of the hole easily and try again. The idea of the pvc float is good also but may need to be built inside tank because it necks down to a 7 inch hole in the top. I will take some pics and try to post them so you guys can understand my contraption a little better. Thanks again.