Pond Boss Forums Thread Like Summary - Air line question.

I have a 1/3 acre pond that's 10' deep I'm trying to setup an aerator for. Its about 500' away from electricity. I was going to try to run power out to my pond, but found on this forum I could just run the air line. I just ordered a Vevor kit that has a 1/2 hp pump, 100' weighted airline, and 10" membrane diffuser. Maybe that was a mistake, I don't know.

My question is what air line would be best to cover the 400' underground? The 3/4 100psi black poly is the cheapest and in stock. Would 1" be better (would have to be ordered), or a heavier pipe? I plan on using a sub soiler behind my tractor to bury it.

All the above is very good advise according to crunched numbers. 3/4" main long line and 1/2" to 5/8" for the diffuser should work well. I have estimated some differences below.

Assuming the following for the completed setup with 3/4" main line and 1/2" diffuser line and a diffuser at 10 foot deep...

Assumptions...

1.) The pump will put out between 2 - 4 CFM at the diffuser.
2.) Running between 8 and 15 psi.
3.) 0.5 to 1 psi to operate the diffuser
4.) Zero losses for valves and fitting since it is a single pump with a single air line (no constricting fittings or valves).
5.) The diffuser line will be 100 foot long.

Pressure loss through the 3/4" line at the low end of the above pump pressure assumption and the high end of the
CFM assumption from...

https://www.engineeringtoolbox.com/pressure-drop-compressed-air-pipes-d_852.html

yields about 1.7 psi. This is the extra pressure that it takes to push the air through 400 foot of 3/4" line given the best conditions of the assumptions.

Do the same for the 100 foot of 1/2" line...

Yields about 3 psi to total 4.7 psi using the best conditions of the assumptions.

Do the same for the higher end of the pump pressure and lower CFM assumptions and you get...

0.2 psi for the 3/4" line and 0.5 psi for the 1/2" line to total 0.7 psi.

The point of the above exercise is to estimate the back pressure on the pump without knowing the actual numbers, using a range of educated guesses. With the above assumptions and quick calculations...the pump would see a back pressure from the 3/4" and 1/2" lines of 0.7psi to 4.7 psi. Lets use the average for a comparable number for later...2.7 psi.

To summarize, the above mumbo jumbo estimates that the system would have about 2.7 psi of back pressure from the 3/4 and 1/2 hoses alone.

If we do the same thing for 1" line and 5/8" line...we get 0.8 psi

How about 3/4" and 5/8" lines? We get 1.5 psi.

So, you can knock almost 2 psi off the pump by using 1" & 5/8" compared to the 3/4" & 1/2". That's a very nice reduction.

You can knock over 1 psi off the pump by using 3/4" & 5/8" compared to the 3/4" & 1/2". That's a good reduction.

A piston pump is a very good pump style and can put out more pressure than the other options (Rotary vane & Diaphragm) hence producing the CFMs you need without killing the pump. Knocking the pressure requirements down on any compressor pump is a good thing for the life of the pump, however.

Once again, the above mumbo jumbo is just to back up the previous good advise from those that know without having to run some numbers...

3/4" & 1/2" line will work with a piston pump.

3/4" & 5/8" works much better.

1" & 5/8" works even better, but would be overkill, in my opinion, given the extra money that would have to be spent for that last 1 psi. This scenario might prove to be a reuired for a rotary vane or diaphragm pump, but not the rocking piston.

Your two main concerns for using 3/4" poly underwater. 1. It will take close to 3/4lb of weight per foot of airline; 5/8" ID requires 0.5lb/ft, thus 100ft weighs 50lbs. . 2. Don't put extra weight on the airline just enough to hold it down because you should be lifting the diffuser out each year and cleaning it. Pulsing the air to the diffuser often does not adequately clean it for good efficient bubbling. Membrane diffusers should have proper maintenance which means a scrubbing each year usually at the beginning of the aeration season - spring.

A couple ways to reduce or eliminate the problem of leaks of plastic tubing at a connector. One is to use two hose clamps with the screw turned 180 degrees of each other. The other is to use a cigarett lighter and slightly warm an inch or two of the tubing. Then when it is still warm, slip it over the connector and tighten the clamp. By warming the plastic it will form fit around the grooves in the connector.

It is best to use car heater hose (NAPA etc) for inside the pump shelter and to get out of the shelter to the ground connection for black poly underground line. Rubber heater bends around tight curves easily, withstands the heat and resists kinking. The problem that I have with the black poly in the shelter is after time you can't get the black poly off the fittings. You almost have to cut them off when you have to do any maintenance on the compressor . With the heater hose it always easily pulls off all connections.