marks
Silver Member
I too have a similar situation; in addition to long distances, the irrigation needs of several acres of landscaping requires an efficient flow of 40 to 50 GPM. Hence, the 2hp well pump is set at 240' and pumps 20 GPM through a 2" PVC line to two 5,000 gallon tanks 400' away with 70' of elevation. A multi-stage pressure pump and pressure tank then serves the house 200' away. Due to the irrigation requirements, there is an irrigation pump that is also located at the water tank.
The reason for the separate irrigation pump was to avoid the frequent starting and starting of the multi-stage pump that would occur if it were to be used for domestic and irrigation purposes. Most wear and tear on a motor is caused during the startup.
The holding tanks, one of which is the minimum code requirement and the other provides for treating the domestic water, allow for the well pump to also avoid frequent starting and stopping. When the pump comes on it will pump no less than 1,000 gallons before shutting off.
Both the lines feeding the domestic and irrigation systems are 2". When irrigating at 50 GPM the friction loss is 4 psi per 100', whereas it is 14 psi for 1.5" pipe. With a 300' length, the friction loss is 12 psi for the 2", and 42 psi for the 1.5” However at low flows, say 10 GPM the difference is minimal.
Essentially it's calculating the marginal friction loss, and the associated energy consumption (that is also charged on a progressive scale), versus the cost of the larger pipe. For me the choice was clear. Here's an address for a Friction Loss table: www.plumbingsupply.com/flowchart.html .
Voltage drop is the same thing but with electricity, I won't bore you with another diatribe. However, it's an important concept so that the motor operates properly and doesn't burn out prematurely. If you need info on the calcs send a PM. If the guy that set my pump had used a slightly larger wire then I could have saved a bundle but not having to run such large cable to the well controller.
Let the required flow, and pump size(s) drive the design.
When laying the pipe consider a tracing wire, in order to easily locate it in the future, you could probably use the controller wire if the pressure switch is at the house. Place thrust blocks appropriately. Regarding the stale water issue, 100' of 2" holds approx 17 gallons.
Hope this helps.
The reason for the separate irrigation pump was to avoid the frequent starting and starting of the multi-stage pump that would occur if it were to be used for domestic and irrigation purposes. Most wear and tear on a motor is caused during the startup.
The holding tanks, one of which is the minimum code requirement and the other provides for treating the domestic water, allow for the well pump to also avoid frequent starting and stopping. When the pump comes on it will pump no less than 1,000 gallons before shutting off.
Both the lines feeding the domestic and irrigation systems are 2". When irrigating at 50 GPM the friction loss is 4 psi per 100', whereas it is 14 psi for 1.5" pipe. With a 300' length, the friction loss is 12 psi for the 2", and 42 psi for the 1.5” However at low flows, say 10 GPM the difference is minimal.
Essentially it's calculating the marginal friction loss, and the associated energy consumption (that is also charged on a progressive scale), versus the cost of the larger pipe. For me the choice was clear. Here's an address for a Friction Loss table: www.plumbingsupply.com/flowchart.html .
Voltage drop is the same thing but with electricity, I won't bore you with another diatribe. However, it's an important concept so that the motor operates properly and doesn't burn out prematurely. If you need info on the calcs send a PM. If the guy that set my pump had used a slightly larger wire then I could have saved a bundle but not having to run such large cable to the well controller.
Let the required flow, and pump size(s) drive the design.
When laying the pipe consider a tracing wire, in order to easily locate it in the future, you could probably use the controller wire if the pressure switch is at the house. Place thrust blocks appropriately. Regarding the stale water issue, 100' of 2" holds approx 17 gallons.
Hope this helps.
