Pump Flow Question - non aquarium

JC565

Hello everyone.

I have a tank/pump question, that isn't actually related to aquarium, but I thought you might be a good group to ask, since you deal with pumps and gravity flow alot.

I have a large tank with some cooling coils in it. This is the secondary tank. The Secondary tank is much taller and is only about half full, which is the same level as max full on the primary tank.

The two tanks are connected together at the bottom by a hose (this keeps the water level even when the system is off) Hot Water is pumped into the top of the secondary tank, (from the primary tank) passes over the coils, and then gravity returns back to the primary tank as colder water, through an outlet at the bottom of the secondary tank. The problem I have, is that the return line doesn't have enough flow under gravity to keep up with the pump. (both are 1" hoses). Eventually all the water is pumped into the secondary tank and the primary tank goes dry.


So.....Here are the options I came up with...

  1. If I were to airtight seal the secondary tank, then wouldn't everything it pumped into the tank, be forced out of the return? (allowing for a little bit of air compression inside the tank since its only half full)
  2. what if instead of sealing the tank, I just keep letting the secondary tank level rise until the water is 2-3 feet above the primary tank. Would this be enough pressure to return as fast as the pump can pump? ( there is a valve to prevent overflow at shut down.) I guess the way to know for sure is to try it, but I don't want to have to drain the water unless I absolutely have too.
  3. just install a 2 inch return line (which would require modification of the primary tank.)


Any one have any suggestions on this? I'm getting a good cooling effect inside the secondary tank, its just not cycling enough water through the system to cool off the primary.


Thanks for your help I hope this isn't too strange of a question for your board!! I do have an interest in aquariums as well. I keep telling myself when I get my forever house I'm going to build something nice.


Thanks again!
 

leftswerve

My vote is 3, bigger return line. There is a formula for how big you need it.
I also think there might be another way, the pump should be in tank 2 at the bottom and plumbed from it's output to the bottom of tank one. As tank one fills, gravity will overflow (your overflow is ath the top of tank one leading to the top of tank two) in to tank 2 on top, and the water will deconvect through the coils down to the pump at the bottom.
 

JC565

My vote is 3, bigger return line. There is a formula for how big you need it.
I also think there might be another way, the pump should be in tank 2 at the bottom and plumbed from it's output to the bottom of tank one. As tank one fills, gravity will overflow (your overflow is ath the top of tank one leading to the top of tank two) in to tank 2 on top, and the water will deconvect through the coils down to the pump at the bottom.
that's how I wanted to do it, but I don't have an overflow that could work. I'm back to modifying the tank. any idea where I might find the formula you mentioned?
 

leftswerve

here's a start, but let google be your friend:
Pipe Sizing Charts and Flow Rates

I should add, you are chasing the dragon, meaning that is a very hard ratio to figure out, much less make work. A gate valve will help you.
 

JC565

here's a start, but let google be your friend:
Pipe Sizing Charts and Flow Rates

I should add, you are chasing the dragon, meaning that is a very hard ratio to figure out, much less make work. A gate valve will help you.
I have a gate valve on the pump slowing it down, but its still far to slow. The intent was to choke it off just a little and set and forget so I don't ever have to worry about adjusting. I think were going to stick a 2" return line in the tank and call it good.
 

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