Pond Boss Forums AERATION Systems questions Aeration Pump and size for 7 acre pond

I Purchased a 3 phase 3/4 hp Gast pump about 3 month ago and found out I don't have 3 phase power by the pond. So now I have to sell that and find a pump for my 7 acre pond. A friend tells me i need 3/4 hp with 4 diffusers. So looking for a pump suggestion and hp size of the pump.
Was going to set the 4 diffusers at about 6 to 8 feet.

Thanks for your help.

Only 4 diffusers for a 7 acre pond?...maybe if it's 30' deep or more. Be careful buying an aeration system based on what the website says it can treat in surface area. There are a lot more factors in sizing an aeration system than just the surface area of your pond and it's always best to consult a professional. If you would like to tell us the max and averge depth, water source, type of diffuser you intend to use, specific uses/goals, shape of pond, and water quality info (if possible), you will get much better feedback.

In general I can tell you that you will get more air for less $ and energy by going with a series of 110V 1/3rd horsepower compressors rather than a single 3/4 HP but the style of compressor you should use depends on operating pressure. Also, you always want to have at least one diffuser in the deepest part of the pond. I hope this helps a little. If you answer the questions above we can give you better information.

Max is 15ft depth - used to be 20ft but that was like 18yrs ago, weed and other build up I would guess.

Don't know avg depth.
Water source - natural spring feed.
Home made diffusers - has 4 air stones on each. Attached a picture of it.
Specific uses/goals = cut back on weeds and aglue growth = prevent any winter fish kill

Shape = hard to descibe - I can send a picture in few days.
What are you asking for on the water quality info? From water tests or if it's clear?

Thanks.

Allmadness,

Based on the preliminary info you've given us: For algae control you should have at least 6 of those 4 port diffusers assemblies spread out throughout the pond making sure to get at least a few of them in the deepest portions of the pond. You should put a ball valve on the air supply line to each diffuser assembly or dedicate a compressor to each diffuser so that you can turn off the deeper ones in the winter to prevent super cooling. I would also attach 8-12" horizontal extensions on the air stone ports with vertical elbows such that you space the diffusers further from the cross member. You will also need a coupler with a 3/4" female pipe thread to put on the elbow to receive the diffusers that I'm about to recommend. Then, rather than putting on air stones, you should switch to a fine-bubble diffuser like the membrane types made by EDI http://www.wastewater.com/aeration-products/disc.htm you can get them out of USA Bluebook for about $16-$28 each depending on if you want to use 9" or 12" (take a look at the spacing between the parallel ports to determine what size you can use). Note: Fine-bubble diffusers are much more efficient than air stones in oxygen transfer and mixing.

In the scenario I described above you would need at least 4 CFM per 4 port diffuser assembly for a total of 24 CFM. This equates to 5-6 1/3rd horsepower compressors (woble-piston style)for a total of 2 horsepower. Be sure to use an oil-less woble piston style rather than rotary vein as the pressures will be too high for rotary vein. I recommend a Thomas 2660 compessor because they handle higher pressures and are durable but they are incredibly difficult to get a hold of these days (although we are expecting 100 of them on Tuesday). In any case be sure to look at voltage, pump curves and ability to restart under pressure when looking for a compressor.

All these parts + additional feeder tubing and connecting components will run you somewhere between $3K-$5K depending on the shape of your pond and feeder tubing requirements. Although I'm baffled at some of the deals I see on this site sometimes so it may be less. I hope this helps. Good luck.....

Thank you for talking the time to explain that all out to me!!

How much are these pumps you are recommending and have on hand?

I was thinking I would run the pump a few hours a day after the startup process? Is that the norm? I don't have a fish dying problem so figured a few hours would just add to the health of the fish.

I don't have a algae problem, i just wanted to get rid of some weeds and help fish with air. The aeration won't kill weeds will it?

Our compressors are $550 and come with an oversized aftermarket air filter assembly rather than the cheasy foam ones that come from the manufacturer. We also include hose barbs, EPDM tubing, hose clamps, and vibration isolators....basically all the connecting components. And, we have the manufacturer change the ramp plates so that our compressors will start with 15 lbs. of back pressure. You could probably find much cheaper rebuilt ones online...ebay or something.

As far as start up goes, there are plenty of threads on this site describing it in detail but generally you start with 15 minutes and then double each day i.e. 15 mins - 30 - 1hr. - 2 hr. - 4 hr. etc... until you reach 24 hour operation. There are other considerations. You should check out the threads.

Finally, aeration will not kill you weeds. In fact, aeration does not "kill" anything directly. Aeration simply changes the biochemistry of the pond such that it discourages the growth of aquatic plants that are generally considered undesireable and encourages the growth of more beneficial species. A lot of times aeration will clear your water and aquatic weeds will grow more since your exposing more of the bottom of the pond to sunlight. Sunlight + water + nutrient rich sediment = rooted aquatic plants (aka weeds). But your fish will love the oxygen and enhanced habitat.

Standard rotary vane compressors (Gast Mfg) work well and have a long life span when diffusers are operated at 15-16ft depths. I have some that have been operating pushing air to 15 ft deep for 17 yrs (1350hrs/yr) and still operating on the first set of vanes 22,950hrs!. Vanes have a normal rated life of 10,000 hrs. Motor bearings rated for 30,000hrs and often 3 sets of vanes.

Wow that's quite a run on that compressor BC! And I suppose you're right, the pressure is not too high for the max rated pressure (10 PSI)of a rotary vane, but it comes pretty close...especially if you consider the friction from the lengths of feeder tubing that would likely be required in a 7 acre lake and the potential for future biofouling and mineralization. I guess I probably should have said that our experience with piston compressors has been better than with rotary vanes in this application. Certainly they both have their upsides and downsides.