positive displacement pump for 30 gallon reservoir?

[phxazcraig]

I've got a 30 gallon reservoir being used in a drain to waste coco system. I'm using all equipment listed in the cocoforcannabis.com tutorials, including a 400gph centrifugal pump.

I have a problem, I think, with the pump moving a lot more water when the reservoir is full than when it is empty. By perhaps double or more. It's causing havoc with my plans for managing EC, and I have wildly different runoff amounts - wasteful.

So I'm looking for a suitable submersible pump with positive displacement so that I get the same amount of water moved per second regardless of water level in the tank. I'm thinking of something in the 300-400gph ballpark, perhaps less. Any recommendations?

 

[freezeland2]

I've got a 30 gallon reservoir being used in a drain to waste coco system. I'm using all equipment listed in the cocoforcannabis.com tutorials, including a 400gph centrifugal pump.

I have a problem, I think, with the pump moving a lot more water when the reservoir is full than when it is empty. By perhaps double or more. It's causing havoc with my plans for managing EC, and I have wildly different runoff amounts - wasteful.

So I'm looking for a suitable submersible pump with positive displacement so that I get the same amount of water moved per second regardless of water level in the tank. I'm thinking of something in the 300-400gph ballpark, perhaps less. Any recommendations?

You are looking for a piston or reciprocating. Both would be external to the reservoir type pumps. I have never seen pumps internal to the reservoir that are not centrifugal. Doesn’t mean they don’t exist, I have never just seen one.