Septic lift pump

If the separate pump chamber can't fill fast enough, then at some point, the pump in it will draw in air, greatly reducing its flow rate.  This would cause long run times.   Note that there is very little pressure pushing water from one chamber to another - so flow rate might be low. 

EST you don’t need a timer , if you have one float switch just shorten the lead wire to about 12” the ball floats turn on off at 45o so you will drop the water level in the tank about 12”  
 We use 3 Floats  a float to turn the pump on , a float to turn the pump off , and a alarm so if your tank is full and the pumps don’t work you will here the buzzer and the red light . 
 1250 gallon tank  with a pump chamber has 2 500 gallon sections and a 250 gallon pump chamber .
 So if you pump down 12” that would be about 35 gallons and you should pump that volume of water @ 3 gallons a minute so 10  minutes  of run time +- 
  What size discharge pipe is coming out of the pump I would think you should have 11/2 main line with 11/4 leach lines .
 leach lines Are designed to run full of fluid  so the leach field get a equal amounts of water. 
  You can only pump the fluid as fast as the holes in the leach lines will let you . 
    You should have a hole in your discharge pipe that will spray down when you pump fluid and let your lines drain in the winter so they don’t Freeze up . 
  This weep hole drains your pipe and relieves   Pressure on your check valve and head on your pump on start up .  John 

Yes , that’s what I’m getting at , the engineers don’t care about drawing down battery’s or how much power they use . 
They want there  manifold to run full of fluid for equal  watering of the field . 
  It’s Possible the manifold is very small and is watering slowly . 
 All so it’s easy to get some thing jammed up in the pipe , the piping sits around and gets dropped in the dirt and dragged around the lengths are 20 ‘ it’s hard to see in there 
The pump would run until the water in the tank went down to the Required level .
 The pump chamber is 6’ tall  the pumps get set up on blocks 4“ and the floats turn on at 3’ And off at 4’ or they get set as far down in the tank as I can reach with out getting in the hole . 
 There should be a pvc union that can be unscrewed to pull the pump up and adjust floats . 
  This check valve works good has a union and you can see it pumping .
   The system is new I’m sure the Installer didn’t Draw a plan on a donut napkin there has to be a paper trail with specs on the system ,a permit would require a plan , board of health requires a plan ? 
  I’m sure the  installer would be more than happy to help you with your system u paid him good money for the work ? 

  After thinking more about your problem i don’t think your field could be  throttle down enough to run for an hour or two .
If your  leitchfield was clogged you would be swimming in your yard . 
   If you buy pass the check valve and it still not pumping as expected  the check valve is not the problem .
   I think Your leach lines are attached on both ends with tees so if a pipe was clogged in the field you would still get good flow . 
    Soooooo that leaves a bad pump ? Or a rock in the line . 
  Is the pump  220 could you be running on one leg of 120 v ? 
  You could check the pipe with a  electrical snake cut the pipe bend a loop in the end of the snake so it Dosent get hung up on the joints 
 push it in the pipe , it will stop when it hits your field or not ? But if it get jammed up 10’ Out or even 50’ short of the field you will know where the clogg is . 

I well it’s time to pull the pump if it Checks out , there is a stone iamed in you main line .
 Your tank should pump down in 10 minutes or so not all day 
 that’s a good size system .
 What size pipe do you have   ?  
 I have a pipe pinger   , when I run a snake down a pipe I can hook the pinger to the wire and follow it in the yard when it stops you have found the clogg , you could have a drain service come out with a  camera and peek in the pipe 

You should be able to rent a boroscope/sewer cam from someone?

t