Water storage tank inlet location

[minerk]

I'm working on a project to add a 250,000 gallon storage tank to our facility to increase our storage of fire/industrial water. This tank will be supplied by our deep well with a flow rate of approx 350 gpm. My question is: Other than maintaining constant head and preventing draining of the tank in the event of a valve failure, is there any reason (codes, etc) to locate the tank inlet above the high level of the tank? As indicated above, this is for fire fighting and industrial use only, so we aren't concerned about treatment/mixing/etc.

 

[PUMPDESIGNER]

If you create sufficient air gap, between the open end of the discharge and the maximum water surface level,
You have the highest grade of backflow prevention possible.
If someone is requiring a backflow preventer to protect the aquifer, then you may be able to eliminate that by the air gap.

PUMPDESIGNER

 

[bimr]

If you have a water line break (besides the valve failure), you may have a situation where you drain the fire water.

On many of these tanks, the discharge pipe for the service water is taken off at a higher tank level (at say the midpoint of the tank) to be sure that the fire water is not used.

 

[BRIS]

The advantages to coming into the bottom of the tank are:

1) The pump head is less at low tank levels meaning the flow is greater always assuming that you don't run off the end of the pump curve.
2) Air is not drawn into the pipeline under negative surge waves following a pump trip.
3) The tank can feed back into the upstream distribution system

None of these advantages will apply to your case and therefore I suggest you make the entry at the top and gain the advantages described above by PUMPDESIGNER and bimr.