A GUIDE TO USING THE PUMP SEARCH DATABASE
FOR RESIDENTIAL PURPOSES
September 30, 2009
www.lightmypump.com
To make the most use out of the pump search database (PSD) you should know how much head you require from your pump. Good water distribution throughout a typical household requires at least 60 psig of pressure at the pump outlet. This amounts to 60 x 2.3 = 138 ft of head. If your pump was using water from a nearby tank you would have to account for the level of water with respect to the pump centerline to get the total head of the pump, this is the head required to determine the size of a pump. If your tank level is 6 feet high from the pump centerline, the total head H of the pump is: H = 138 - 6 = 132 ft.
What flow rate do you require? Well, that’s up to you. Maybe you want your bathtub to fill in 3 minutes instead of 10. Or maybe you have a special shower with multiple heads requiring allot of flow, you should determine this. Most households will be content with 10-20 USgpm. Why USgpm, this is the flow unit used by all pump manufacturers in North America. However there is the Imperial gal per minute (Impgpm) which for the same volume has less gallons. These units are used in Canada, the United Kingdom and others.
Very often, the house owner will be drawing water from a shallow or deep well. If so determine the depth of water from the pump centerline, if it is 15 feet down then the total head will be: 138+15 = 153 ft. Normally a conventional jet pump will handle a shallow well 15 feet deep. If your well water level is 150 feet down then the total head will be 138 + 150 = 288 ft and you will need 4” vertical turbine pump to do the job, assuming you have a 4” borehole pipe.
So to help your search do some preliminary calculations on the flow and total head required. You will get better targeted results from the PSD.
Be aware that the retailer may not know how a pump works and that the total head and flow are the critical factors affecting the size and performance of the pump. In particular, the total head given may be the maximum head possible. At the maximum total head, the pump has zero or little flow, what you require is the head at the flow you wish to operate or close to it. This applies to all centrifugal pumps whether they are a centrifugal jet type (http://www.femyers.com/products/watersystems/jet%20well/MPN_Series.html) or vertical turbine (http://www.nocchi.it/modello.asp?I_ID=24). It does not apply to piston pumps (http://www.pompco.com/default.aspx?idPage=13) such as supplied by this manufacturer. Piston pumps can provide more pressure than you will ever require. Their main limitation is flow; they are purchased on the basis of flow ONLY.
You will require an air bladder reservoir connected to the outlet of your pump. These are commonly available where pumps are sold. This is to keep the pump from stopping and starting every time a tap is opened.