Pond Boss Forums AERATION Systems questions Air pump question

I have an old 1/2 acre pond that I ran power to and installed a pump and two diffusers as a quick fix. I am now ready to install a better permanent system.
The diffusers are these: https://www.amazon.com/gp/product/B01G4BLYKS/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
They are installed with ~175' of 3/8" sinking hose in about 8' depth
The pump I used was this: https://www.aquacave.com/eco-plus-7-commercial-air-pump-280w-200l-min.html
The specs on this little pump say 7CFM and it has worked for the last year. How is it possible that this pump can put out 7CFM when a more substantial pump like this is rated at 4.5 CFM: https://www.123ponds.com/src50.html...zr9jmnhQtVr4_6ZdCSTHidkt8GoaAr4DEALw_wcB
What am I missing here?
the little pump is ~.375 HP, 280 watts, 200L/min and cost about $130 when I bought it.
The one I am looking at is 1/2 Hp and about $650.00
Thanks in advance for any answers

The EcoPlus is a diaphragm pump and will put out the advertised 7 CFM without anything hooked up to it. It's a "maximum output" that is deceiving since adding a line, a diffuser, and dropping it in 8 foot of water puts some resistance on the pump and that resistance will reduce the actual air flow through the diffuser. You need to locate a pump curve for the EcoPlus 7 to determine what the pump is putting out in in your scenario.

The rocking piston pump is very robust and can create much higher pressures, hence maintaining a much more consistent air flow in deeper waters. The SC50 only loses 1 CFM from the water's surface down to 15 plus feet of water depth. The EcoPlus will surely give up producing air by the 10 foot level.

I cannot find a curve for the EcoPlus 7, but did find the maximum pressure. At about 7psi, the pump stops pushing air. That's about 10-11 foot of water given 2 psi of line and fitting loses. So, my guess is that it is putting out about 2 CFM at your 8 foot depth. Pretty good, really, for a single diffuser system. The SC50 can produce up to 30psi and still deliver about 3.3 CFM. This piston pump would be good for deeper waters and/or multiple diffusers.

Thanks for the quick reply and sorry about the late response. You must be an engineer. I take it from your response that this pump may be overkill for my situation even though I do have two diffusers. I believe the deepest spot in my pond to be about 10' and most of it is 6' to 8'. Should I be looking for something a little less robust? I appreciate your input.

The SSI diffusers you have linked are spec'd to flow 0-12 CFM. I would worry about running them at the max of 12 CFM, but they should easily handle 2 to 5 CFM. Keep in mind that I am not familiar with the quality of the SSI diffusers, but just by looking at the specs...they can take some air flow. Same applies with the quality of the SC50 piston pump...I'm just not familiar with either brand.

I believe you are right in looking for a better pump to run two or more diffusers. The EcoPlus 7 should be an affordable entry level pump for a single diffuser at 8 foot depths. The SC50 piston pump would operate your diffusers in a much better fashion. The max flow of the SC50 would work very well with two diffusers at about 2 CFM per diffuser, placed in 10 foot of water, a bit more CFM if in 8 foot, but still within the diffuser specs. It's a good choice for what you are doing.

You might save some money by looking at the rotary vane pumps. The Gast brand gets a lot of kudos here at PB and is what I use in my pond. The Gast 0523 model 1/4 Hp pump would be the right size to check into. It's been a while since I purchased mine, so the price has surely gone up. It won't pump air to the depths that the piston pump would , but at 10 foot of depth, it would produce similar air flow as the SC50 and is a very reliable pump that can be rebuilt rather easily given it just wore out.

Another option would be to look in to going the cheaper route and getting two of the EcoPlus 7's (or a larger model) or research the equivalent in the HiBlow brand. There are plenty of people using the HiBlow's to areate their pond. Both are diaphragm pumps that can be rebuilt easily, but diaphragm pump curves typically indicate that they are not the best suited for pumping air down to 8 to 10 foot depths. Meaning, they lose air flow in deeper water and would be operating outside the manufactures recommended pressure spec. A generic statement, but pretty typical.

My advice would be to stick with the piston pump or the rotary vane. They do produce more noise, but are more reliable. Some say that they consume more electric than the diaphragm pumps, but being a mechanical engineer...electrical concepts are more challenging...lol

Thanks again for letting me pick your brain. I find it interesting that the Gast 0523 is rated at 1/4 HP and uses 190 watts of power as opposed to the diaphragm pump (the Eco Plus 7) which uses 280 watts (both at 120 volts). Seems like the Gast pump will not only pump more air at depth, but use less power to do it. Making it cheaper to run and with better results.
The Gast pump also says 127 L/m while the Eco Plus says 200 L/m. So what it boils down to is one needs to see the pump curve. So I have, once again, learned something new. Thanks for taking the time to educate me!
By the way, that little pump produced a boil on two diffusers all last summer and fall, and all spring until now. So it is no slouch.

Steve

The gast pumps are a LOT easier to rebuild when that time comes too. Just remember that if you are doing a DIY system, you have to figure out a way to put a real air filter on the inlet side, keep the pump out of the rain AND keep air blowing at it to keep it cool. Not only the Gast but all the compressors.

On the Vertex Brookwood compressors, they have a washable polyester air filter that is inside a sort of muffler to deaden the intake noise, and they recommend washing/cleaning the intake filter every quarter.

Thanks for the tips.
Steve

I bought and installed the Gast 0523. It works much better than what I had and I have two good sized boils going now. It only pulls about an amp more than what I had and soundwise is much less annoying. It is running right at 10 PSI which I believe is the max allowable for this pump. Is that something I should try to remedy? I am using 3/8" hose which I could change out, but was wondering if adding a third diffuser would do the same thing.
Thanks,
Steve

Steve, depending on the length of run and the depth of the diffusers, you could see a pretty good drop in psi. Maybe an extreme case, but when I swapped 3/8" for 1", then necked it down to 1/2" going into the pond at a customers I saw a 6 psi drop in back pressure.

The big pressure thief is likely the 3/8" line, especially if they are long (longer than 50 foot each, thereabouts). Going to 5/8" line will make a nice difference with just the 2 diffusers. The Gast 0523 can certainly run 3 diffusers so long as they are no deeper than 10 foot each and have 5/8" ID line. That's my 0523 setup...5/8" line, one at 70/80'. the other 2 at 50/60 foot, and the deepest at 7'. It runs at 5-6 psi. Your not at a pump "kill" scenario at 10 psi, but you could do better and add some life to the pump. I would not stress about it, but adding 5/8" line would reduce your back pressure and, likely, increase the overall airflow.

Thanks. I have pretty much come to that same conclusion. I'm going to swap out the line and get that pressure down some.
I appreciate the input.