Pond Boss Forums AERATION Systems questions Air line size for long runs?

First I would like to thank Ted for all of his help and advice on my aeration system. I have been putting the equipment together to run’’OVER kill’’ aeration to our pond. I am running a Gast # 0523 ¼ hp rotary vane compressor pushing 4.2 cfm open flow at 10psi.to a vertex membrane quad diffuser. The questions are this! I have a run of 440 foot to the pond for the air line. I had all intentions of running ½ black poly but am not sure if that is going to give me the 4.0 cfm at the diffuser? Should I run ¾ or perhaps 1 in to get a true 4.0 cfm at the pond thus reducing back pressure at the pump and prolonging the life of the pump vanes? From doing (attempting to do ) the liner math I come up with only being able to delivery 2.0 cfm running 1/2 poly. Thanks for the help!I hope some day to be able to add to the board and not just ask questions. I am going to take pics of the project and keep a log.Ps the depth of the diffuser will be around 8 to 10 ft and the over kill is to carry fish in drought and to help with a nutrient rich pond. I have stopped or slowed the phosphors and nitrogen load by limiting my farmer on what he can spread on the field, when, and where. He had the choice of stopping the tractor trailer loads of chicken poop and lime or give up the land. So we are going to switch from corn production this year to beans, plant a 30ft buffer( warm summer grass and pine) zone around ponds and run off swale (swale catches run off and funnels to ponds) between aeration, chemical treatments, and reductions in run off I hope to limit the FA to a normal levels. Now If I can just weasel the 3500.00 out of the budget lady for a 6in well I will have some of what I need for the pond!

Salt,

I haven't had an opportunity to do the math but here is a link to a post that almost mimics your situation. In this thread, take at look at BZ's post.

http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=11;t=000148

What size tubing did Ted suggest you use??

Ok, I just did some quick math and hopefully the experts will check and correct my calculations.

Friction loss for 0.5" tubing is 0.16 psi/100':

0.16*4.40= 0.70 psi

Water pressure is 1 psi / 27" of water:

10' (depth of diffuser) = 120"/27 = 4.44 psi

Total pressure so far is around 5 psi. Like BZ stated in his post, you will have some backpressure from the diffuser. According to my chart, a Gast 0523 1/3 Hp compressor will yield 4 cfm at 5 psi. It will yield around 2 cfm @ 10psi.

You posted "......compressor pushing 4.2 cfm open flow at 10psi." I believe your compressor will only produce 4.2 cfm at open flow. At 10 psi, the cfm will be about half that. Double check the product performance chart.

Final thoughts; like BZ stated, don't skimp on the pipe size. 1/2" tubing looks borderline. I would use larger diameter tubing, like 1", so that when you expand your pond later, you'll have the extra capacity for that additional diffuser you are going to add.

is that SCFM or ACFM that you are trying to achieve? if we assume Ulster is at sea level then you will have approximately 75% of the flow at the bottom of the pond that there will be at the surface of the lake (think about how the bubbles get bigger as they rise) even tho its all the same air.

i presume your friction loss is an assumption

Thank you gentlemen. I will be using ¾ black poly all the way to the pond ½ supply to the diffuser. Next question! The hole coming out of the compressor is ¼ npt. I am coming straight from ¼ to ½ to ¾ for my manifold. Then ¾ all the way to the pond . If I made my manifold out of 3/8 or ½ then went to ¾ nipple would the restriction at the pump effect the whole system? Or would the air from the pump going right into the bigger line negate the restriction at the manifold?

The latter is correct Salt. With using the larger 3/4" line you are trying to reduce your friction loss in that long of a line. The 1/4" is kind of like putting your finger over the end of a hose to increase the pressure. You will get the air (or in this example the water) to shoot futher without any more restrictions.