Pond Boss Forums Thread Like Summary - Sizing trash pump and hose for filling/maintaining

Hi Folks.

I have a 1/2 acre pond that has less than ideal catchment area so want to get a pump and hose setup so I can maintain levels from a local river during dry months.

I have 30ft uphill and 325ft total run to reach the pond.

My current 125gpm 2" high pressure pump and 2" poly pipe setup is very slow during refills. Suspect both from it being an HP pump and long run of hose. I'm probably only getting 75gpm out of it.

If I go with a 3 or 4" trash pump, would I want to use a bigger discharge hose diameter than the pump to account for the 30ft lift and 300+ run? I'd like to get the most of whatever pump I purchase so would like to ensure I get a low friction loss setup to get max gpm. Ideally 200-300gpm would be great.

Please let me know your thoughts on this.

Thank you!

Frictional pressure losses in pipe are very dependent on pipe diameter (as you imply).

It is also fairly dependent on flow rate. Sometimes bigger is not MUCH better, especially if you are trading off money for time.

Pressure drop estimates for 300' run of plastic pipe:

Diameter GPM Pressure Drop
2" 300 169#
3" 300 24#
4" 300 6#

2" 200 80#
3" 200 11#
4" 200 3#

Those are ballpark estimates for straight pipe only. I hope that is sufficient information for you to start planning your project.

Those figures are for the frictional pressure losses only. You will have to add in the additional work required from your pump to lift the fluid as required for your elevation changes. (In general, place the pump as low as possible on the suction side to your water source. "Pushing" the water is usually far more efficient on the discharge side, relative to "sucking" the water on the intake side.)

Good luck on your project!

Frogger,

A centrifugal pump has variable output depending on the head. There should be a pump curve that you can reference to find that number. Some portion of that is lifting water. Keep in mind that there is more to it than just from the discharge to the pond. One must also include lifting water to the pump itself on the suction end. This has its own curve. As a general rule, keep the discharge and suction conduits the same diameter as the those on the pump. Restricting a 4" pump to 2" will greatly increase the head resulting in lower flowrate. A lower cost conduit that would probably work well with a 4" pump is the flat irrigation tubing. Its very affordable for long spans.

BUMP***

Don't overcomplicate this. You have a reference on your 2" pump at 75 gallons per minute. A 4" pump that has similar head limit will produce ~4x that rate provided you give it 4" conduit. It will probably not be worth putting 4" hose on a 2" pump though it would increase flow by reducing the frictional loss. Were it me, I would make the decision based solely on the benefits of pump size and size the conduits accordingly.

A 2” trash pump with 2” hose, will raise your pond 6” in 24 hrs.

I don't see why the corrugate pipe wouldn't work. You will probably need to couple 100 ft pieces. The flat is pretty easy to lay and even easier to put up but probably has a more limited life span as you suggested. It's your choice. Keep us posted on your choice and any further thoughts after implementation.

Bumping the discharge hose/pipe size up 1" above the pump discharge outlet is a good idea. If this will be out in the weather for the season (or more)...the corrugated pipe would last longer compared to the run-of-the-mill lay flat hose (think sun/UV damage). I would definitely use the lay flat hose IF this is a system that will get stored away regularly AND the hose is running down hill. Sometimes these lay flat hoses can get to rippling which causes it to pinch, especially if running up hill or over uneven ground.

Frogger,

I was doing a project very similar to your project - and reached the same conclusion that black corrugated drain pipe was far better on price and diameter than blue lay-flat.

However, whenever I think a product is better than the common solution, I start worrying that I am missing some important physical parameter. I actually called the distributor for Menard's black corrugated drain pipe and asked about my application. He said that their product is definitely NOT DESIGNED for that application. Once he determined that I (sort of) knew what I was talking about, he said there was a chance of making it work, but he again stressed that was way out of their design.

As I recall, he thought the biggest problem would be connections. Their "soil tight" connections in the drain pipe application are designed to keep the water in and the soil out at pressures very close to 0 psi. Once you start pumping uphill, your head pressures are no longer near the 0 psi design parameters for drain pipe. (Even though I am pretty sure it has a "burst strength" far above your head pressure.)

I ended up using PVC and blue lay flat. That was a no-drip combination in my application, and I just have to do a little work with the lay-flat when I need to pump water on that "occasional use" system.

Good luck,
Rod