Grid-Connect Underground Water Storage Tanks?

12/16/2021

I'm performing a shop drawing review of underground concrete storage tanks, to be used for firefighting.

We have six tanks arranged into two rows of three. 12-inch pipes connect the three tanks per row toegether, and one 12-inch pipe connects the two rows at one end.

It makes a U-shape flow path down one row, and back up the other.

Should two more linking pipes be added to form a complete grid, and allow more paths for water to flow?

Should these linking pipes be provided with vortex plates?

Thanks in advance!

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6 Comments

MIke L

12/16/2021 07:02:42 am

Assuming the tanks are all in close proximity to each other, the additional pipes would not provide any benefit performance wise. The tanks should empty at an equal rate with the pipe layout you have.

The additional equalizing pipes could be installed as a "belts and suspenders" approach in the event something happens to the primary discharge pipe, you have an alternate pipe to maintain the water supply.

As far as the vortex plates go, if the tanks are supplying a pump, then they must be installed. Otherwise, I would just keep the discharge pipe an inch or so above the bottom of the tank.

Glenn Berger

12/16/2021 08:12:13 am

Something not mentioned - Ensure that there are valves such that one tank can be taken out of service w/o degrading the rest of the system.

Alex

12/16/2021 08:18:50 am

Hi,

Adding the additional piping would not increase flow but would provide redundancy within the system. If a single pipe would fail, you would still have water flow available while replacing the broken line.

Like Glenn mentioned above, ensure you have isolation valves installed.

Alex

sean

12/16/2021 09:06:46 am

sounds like additional complexity with little benefit

Anthony

12/16/2021 09:20:57 am

Great comments above!

I can't see any performance increase here that would require the need to grid the tanks. You could always do a very back of the napkin check and dust off your hydraulics text book do a Bernoulli D/T tank calc and figure out the time it would take the tank to empty given its geometry and orifice cross section area driven by gravity vs the pump suction rate. This would tell you if your 12'' pipe is large enough. Not sure what volumes and flow rates you're dealing with.

Adding to Glen's comment: I think a circular feed or loop would be a better idea than a grid. This way any one tank can be isolated and you're back at your U shape feed. Though it would require a valve between each tank.

Lastly Its always a good call do lower the complexity of a system that is underground or hard to access. Every cross connection is a failure point, make sure you need it before you add it.

Jack G

12/16/2021 03:20:21 pm

Add valves to isolate. Looping is good. If it’s for fire fighting purposes, I d assume some sort of pumper truck which could create virtexind and an air column above the tank discharge, assuming a bottom discharge to get all of the water from each tank.

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Grid-Connect Underground Water Storage Tanks?

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