Pressure tank drawdown chart manual#

Thus the tank should be sized to handle at least one minute pump run time. As stated earlier the start and stop is what wears the pump. I’m no expert but I believe submersible pump manufacturers state the pump should run for a least a minute when it starts. So your tank at 40 gallons should not have that much of a different drawdown.) (Notice the WR140 in post #2 is a 44 gallon tank and has a drawdown at 30-50 of 13.6 gallons. You can see that these factors are universal and if you apply them even to the chart in post #2 you can see they work. Here is chart with drawdown factors:ĭrawdown Factor Chart | WELLMATE Composite Water Storage Tanks So your calculation would be 40 gals x 0.30 = 12 gals drawdown. That is, you multiply 0.30 times the tank volume (that’s total tank volume) to get the drawdown number. At 30-50 I believe the drawdown multiplication factor is 0.30. Looking for the benefits of having a properly sized pressure tank in your home? Call us today at RC Worst & Company to help you choose the right tank.Frank are you sure your tank is 40 gallons? If so I think you should be getting more than 5 gallons drawdown.

Pressure tank drawdown chart manual#

Consult your manual for manufacturer recommendations on tank size. Note: The above calculations should not be used if you have a variable frequency drive in your system. Pumps with flow rates up to 10 GPM should have a tank with a minimum of one gallon drawdown capacity for each GPM delivered by the pump. This should not be confused with “tank volume.” For example, a pre-charged tank with a tank volume of 20 gallons has only five to seven gallons drawdown capacity depending on the cut-in / cut-out (on/off) setting of the pressure switch. Tank drawdown capacity is the minimum amount of water stored and/or delivered by the pressure tank between pump shut-off and pump re-start. Tank drawdown capacity required = Pump flow rate multiplied by run time The pump turns on when the system reaches the low pressure cut-in and off when the high pressure cut-in is reached.įrom these factors you can determine drawdown needed with the following equation: Cut-in and cut-out psi (pounds per square inch) of the pressure switch. Pump flow rate in gallons per minute (GPM)ģ. To determine the proper size of the pressure tank, there are three factors to consider:ġ. One horsepower and larger pumps require longer run times. Most manufacturers recommend a minimum run time of one minute for efficient motor cooling. A larger drawdown means longer run time and therefore less cycles. The bigger the tank you have the larger the drawdown (actual amount of water stored) you will have. When the low setting is reached the pressure switch tells the water pump to turn on and more water is pushed into the tank and house. The water is pushed throughout the plumbing in the house until the pressure drops to a preset low on your pressure switch. When a valve is opened, water is pushed out by the compressed air in the tank. When it comes to pressure tanks, bigger is almost always better.Ī pressure tank creates water pressure by using compressed air to bear down on the water. It increases energy use and can cause premature failure of your pump as it builds up excessive heat.

Short cycling is a term used to describe when your pump is turning on and off too frequently. If you fail to invest in the correct size pressure tank, you can short cycle your pump. Choosing the proper tank for your pumping system will greatly reduce the risk of premature pump failure.

If the answer is yes to either of the questions above, it is important to have the correct sized pressure tank for your system. Would you like to save money by reducing energy use? Would you like to prolong the life of your pump?