Submersible pump in vacuum tank

[Russ]

We have reworked out vacuum system as some of you recall from previous postings. We're going to a thermostatically controlled switch to start and stop the vacuum motor, as one of our sugarbushes is 20 miles from my brother's house. We have a 300 gallon Zero tank as our vacuum chamber/collection tank. In the past we have used a submersible pump with a float switch inside the tank to pump sap out to a larger (non-vacuum) storage tank. We probably never had a decent vacuum on the tank, but we think we have rectified that situation. Some area producers are of the opinion that with a good 20"+ vacuum, the submersible pump will not be able to push sap out of the vacuum tank. I think its a 1/3 or 1/4 horse Wayne pump, pushing sap out through a 3/4" poly line with a check valve. Anyone else doing this?

[maplehound]

Russ, What the others are telling you about your pump not being able to pump against the vacuume is true. The only pump I have found that can is a deep well pump. I am also using a 300 gal zero and I have a 120 volt deep well pump in mine that is connected to a float valve that empties the tank when it gets full. Most pumps wouldn't put out enough pressure to overcome the vacuume. As a plumber friend of mine has told me you need 2lbs of pressure for every foot of rise. In this case you would need 40 lbs of pressure just to get the sap to the top of the tank and then 2lb of pressure extra for every foot of rise from there. Most Deep well pumps will pump water 150 feet or more up to the top of a well. Therefore they have more than enough pressure to overcome the vacuum.
BEEN THERE DONE THAT AND AM STILL DOING IT!!!!!!!!

[Acer]

14.7 psi (full vacuum)is about 33 ft of head.
Took a quick look at wayne submersibles and the 1/4 horse wont do it at 25' of head. Deep submersible well pump is your best bet.

[brookledge]

I have a vac. tank that I have a 1 HP well pump on it and it can overcome the 20" of vac that I have on it. You can definately see it pump slower when the vac is on vs. when it is off.
Your other option is to shut off the vac. when you need to pump out the tank but not the best practice.
Keith

[michiganfarmer]

Ive wondered this same thing.

Interesting responces

[Teuchtar]

One idea might be to energize a solenoid valve to bleed air into the vacuum tank making the vacuum rise to, lets say 5 inches of vacuum. That should be enough to allow your submersible pump to override the vacuum.
The solenoid would be wired in parallel with the pump.
When the pump stops, the solenoid closes and your vacuum pump can draw the tank back down to 20".
That would require some tinkering. But also creates hours of endless fun.

[maplecrest]

back when i used my vac tank i had a dairy receiver jar pump hooked to the bottom drain port with a float switch in the tank. it work great. the pump had to pump to the sugar house across the yard from the old milk house. i found that with the pump below the sap level of the tank there was no problem pumping against the vac. the distance pumping to the storage at the sugar house was the challenge