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Dewatering Pump

Dewatering Pump

Dewatering Pump

(OP)

We have an atmospheric pressure underground tank 8ft L X 14 inches W X 3 ft-4 inches deep ( 233 US gal capacity) .The bottom of this tank is 21 feet below the ground level. Water is seeping into this tank from surroundings at the rate of 0.3 gpm. It is a requirement that this tank should be continuously dewatered and preferably should be free from any water. The water is to be pumped into another adjoining atmospheric pressure tank 2 feet above the ground level by a flexible rubber hose.

I had thought of sump pump like Flygt SX 3(max head 34 feet) but this leaves about 4” level of water behind.

Could any pump guru suggest any suitable submersible, suction or other pumps for this application. Both electrically and air driven pumps could be used. Flow of pump is not important and could be say 5-10 gpm @ 27 feet. Width of tank could be changed to a maximum of say 20 inches. Pump shut off pressure should not be more than15 psig. The arrangement is required to work satisfactorily for about 4- 6 months.

Thanks

RE: Dewatering Pump

If you put a boot on it, does the boot have to be kept water free?  4" or so of water in a boot isn't much.

RE: Dewatering Pump

(OP)
Hi
Thanks for your response.This is an existing tank and nothing can be done about it.As mentioned earlier this tank needs preferably to be kept water free so that there is no potential of leakage into the adjacent area.

RE: Dewatering Pump

You will probably need some form of positive displacement or flexible vane pump with good suction strength. Since it can be a small unit, I'd suggest March or similar pumps, or see what's available in marine bilge pumps that can run continously

www.marchpump.com

Keep the wheels on the ground
Bob
showshine@aol.com

RE: Dewatering Pump

(OP)
Hello Sprintcar, Showshine
1.I checked the March Pumps from the web site.Series 5.5 seems to be too high( 40 feet head) and Series 5 seems to be insufficient( 28 feet head)as we have to limit the system to be below 15 psig due to local regulations.Any otther suggestions/vendors?
The pump will be kept on the floor but that will leave about 4" water level unemptied.Any suggessions to drain off completely?
2. We also want the pump shut off pressure below 15 psig so that the system is not required to be registered by local authorities here which is a cumbersome and lengthy process.

3. What should be velocity limitation on the discharge hose( rubber).Is 7 to 10 Ft/sec acceptable? With this limitation I am getting pressure drop of about 30' per 100 feet.Is it acceptable?Hose length is 25 feet.

Raj


RE: Dewatering Pump

Hey raj check out guzzler pumps by bosworth company;)

RE: Dewatering Pump

Why don't you try using the larger March pump and just put some sort of discharge orifice in the line to break down the had to the levels you need.  Sure, this is wasting electricity, but the amount of electricity and the cost of the "waste" is relatively small....definately within tolerable limits to most.

I know this isn't the *best* option, but it would work and be inexpensive.

Tim

RE: Dewatering Pump

Hi, there are a few options to try, 1st a diaphragm pump will suck down to the floor without a problem. try http://www.pump-shop.co.uk where this is loads of info on this type of pump, or 2nd you could use a 'puddlesucker' submersible from W Robinson http://www.pump.co.uk The benefits of an air pump are, that it will run dry and can be submerged or not. the disadvantage is that air is dearer than electricity. Hope this helps :)

RE: Dewatering Pump

There is a Tsurumi Electrical submersible water pump model LSC which is capable of pumping water down to a minimum level of 1mm.  pumping capacity at 0.8 m3/min at 10 meter. shut-off head = 12.5m.  weight 14 kgs. 0.4 kw single phase, 50 hz, 220v. you could contact 065-68411192(singapoe) for further enquiry

RE: Dewatering Pump

Dear Raj200,

It seems the bottom of the underground tank is flat.
When we are using any centrifugal pump to dewater, it can pump only up to certain level, depending upon the NPSH R. If the pump is operated below that, cavitation will start.

When you need to have a complete dry surface of the tank, you must have a small collection pit in this tank with little slope may be at some corner and install a pumpset in that small pit. The size of the pit shall be designed based on the dimensions of the pit. This will clear all the water from the srface and you can get a dry pit bottom.

the model and sizing of the pumpset will depend upon the total water to be pumpsed out and the seepage. this is the only and easiest solution.

Rajendra

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