Using Lake Water for Fire Pump Supply

[gfire]

When using a lake or pond as a water source for a sprinkler system, what is the best way to go about doing it. This is my first project where city water is not available.

The lake is lower than the buildings, and according to NFPA 20 6.1.2 Centrifugal pumps shall not be used whre a static suction lift is required.

The architect wants the pump up by the building, but I think it needs to be a vertical turbine pump in a wet pit (something like NFPA 20 Figure A7.2.2.2) down next to the lake.

If they insist that it can't be next to the lake then my next thought is that we will need to bury a tank somewhere, which seems like a waste when the lake is available.

Any thoughts or suggestions?

 

[pipesnpumps]

You are on the right track.. Submersed vertical turbine.

I've seen alot of private fire pumps, and they are always this way. Sorry I don't have NFPA 20 handy but it should bear this out. Footvalves are notorious for failing which would mean a centrifugal pump couldn't prime, which would be a bad day...

Architects are too concerned with image. They all want to build momuments to themselves....

Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.

 

[SprinklerDesigner2]

Depending on the design standard that buried water tank could be big and you would still be using a vertical turbine pump.

Photos show wet well for a 1,500 gpm pump during construction. Kind of an ugly pump house, for a cotton warehouse in the middle of nowhere, but it was done right and it worked.

http://img405.imageshack.us/img405/1410/pump1p.jpg

http://img600.imageshack.us/img600/2637/pump2.jpg

http://img856.imageshack.us/img856/2603/pump3.jpg

http://img849.imageshack.us/img849/8062/pump4j.jpg

http://img535.imageshack.us/img535/6075/pump5.jpg

http://img850.imageshack.us/img850/9038/v7m.mp4

 

[DavidCR]

Diesel engine powered vertical turbines, on wet pits on natural water sources or ponds have a big probability of cooling system problems, if the pit is not designed with extra precautions to prevent debris to clog the cooling systems.

I´m not sure if an air cooling system can be accepted on diesel engine pumps to solve this.

Anyway, try to obtain a good civil engineer that handle with good criteria the design of the pit to prevent dirty water problems, plastic bags, fishes, snails, plants, seaweeds, etc. can ruin your suction in surprising ways.

 

[chicopee]

I agree with pipesnpumps. Electric pump and diesel as a backup.

 

[chillylulu]

Another consideration is that you will need to gooseneck all of the sprinklers in the building:

NFPA 13, 2010
8.15.18 Return Bends.

8.15.18.1 Unless the requirements of 8.15.18.3 or 8.15.18.4
are met, return bends shall be used where pendent sprinklers
are supplied from a raw water source, a mill pond, or open-top
reservoirs.

8.15.18.2 Return bends shall be connected to the top of
branch lines in order to avoid accumulation of sediment in
the drop nipples in accordance with Figure 8.15.18.2.

8.15.18.3 Return bends shall not be required for deluge
systems.

8.15.18.4 Return bends shall not be required where dry pendent
sprinklers are used.


There are a lot of considerations that go beyond the scope of most sprinkler designers when taking the supply from a pond or lake. They include:

1. Environmental considerations - how do you protect the lake from fuel, oil, etc. Even hot water discharging from a diesel pump heat exchanger can be an issue.

2. How reliable is the water supply? Does the water level change seasonally? Will a prolonged drougnt affect the water supply? Are there concerns with freezing? Is flooding an issue?

3. How much water can you reliably take from the source? Can it meet the water supply duration?

4. How do you protect the system piping from MIC (microbiologically induced corrosion?) This is more important than it used to be. Lake or pond biology can change. How do you know that it won't affect your piping system?

5. Future cost of maintaining a vertical turbine pump, including future regulations, maintaining the suction area, pit cleaning, etc. The real cost could be much more than the cost of a tank supply.