Hey all, I have a solar DC aerator I installed last summer late in the year. Highflyer has helped me with upgrading some of the components but I've had an issue surface I need help with.
I has been running up to 6 hrs a day here the last 3 weeks, but a few days ago while at pond I noticed no boil in the water.
Pump was running, checked above water lines-no leaks. Shut pump off and pulled line off of pump-loads of pressure-put line back on started pump and had airflow again...for about 20 min. it slowly fell off to nothing-not a bubble with no change in pump sound. Pulled diffuser and it works on land. As soon as I drop diffuser over side of boat bubbles quit.
I have Vinyl line above water and weighted from water line on. I disconnect line at barb between vinyl and sinking line-tons of pressure. I disconnected line from diffuser today and noticed I can stop flow with my tongue, so I "think" I have something going on inside my weighted line. Could algae build up with no check valve and create a blockage???? Then flow back open when water seeps back up??
I forgot to mention I installed a complete new pump/motor combo with the same result. This is getting expensive messing with DC aeration but I'm a LONG ways from REA.
I should also add this was installed late July last summer-worked great. Worked great the first several weeks this year also.

snipe, any chance your weighted line is full of water?

So something is causing the back pressure on the line to be greater than the PSI the pump can produce. What is max PSI for your pump? Do you have a PSI gauge installed? If not, that would be step one for me. Do you have a pop off valve installed? Speaking from personal experience on what has increased the back pressure on my lines - condensation. It came on slow and gradually eroded performance. Do you have any big dips in your weighted line? It's probably not that though, seems I am the only one that's ever had that problem.

I had one of my three lines get water in it during a shut down period...pulled the line out, unhooked the diffuser, drained a gallon or two out, put it back in the pond and it's been working fine since.

In January I experienced some water condensation in one of my air lines to a diffuser. In my case a seller's description of the air hose as "weighted" was inaccurate. I used a series of bricks to weigh down the line. Despite using six to eight bricks along a 50' hose run, the line tends to float between bricks. This resulted in "humps" and places for moisture to condense. I observed almost no airflow from that diffuser in January and the pressure gauge showed an increase of about 1.5 PSIG above normal operating conditions. I pulled the diffuser and let it "vent" for about one hour. Upon returning the diffuser to the water, the pressure reading on the gauge returned to normal and airflow from the diffuser returned to normal. It doesn't take much water in the air line to begin choking off airflow. If a piece of debris somehow becomes lodged in your air line it would have a similar effect. A gauge is your friend in helping to diagnose pressure changes. I use the gauge to determine a baseline pressure and if that pressure indication changes, I know something needs investigated. In a way it can be counter-intuitive-- increased pressure on the gauge can mean decreased airflow. And in my case- a partially obstructed air line from water condensation. All good tips from others that replied too.

I had a problem like yours a couple years ago when restarting one of the diffusers that was shut down for the winter. What ever the problem was, between the diffuser, the check valve and 200 feet of hose, I can only guess.

Here's what solved the problem...
I put a portable air tank in place of the pump, and slowly increased the pressure. problem solved, not another issue since.

Tracy, it back fills every time it shuts down. It takes 3-5 secs after pump comes on to seeing air.
I've had the entire weighted line up on the bank and walked it "up" to drain any water. I've unhooked line from diffuser and pumped air, it seems fine but I can tell pressure is not as high through weighted line as it is before weighted line.
I dropped weighted line without diffuser installed into 7' of water and it pumped free air for 15-20 min then dwindled off to zero, never noticed any change in pump sound. I've pulled it out and ran with line on bank, hooked diffuser up and set in 2' of water. Ran for about the same amount of time and air slowly stopped with all but 4' of line up on bank.
I suspected a pump problem and spent the 300$ on a new motor/pump and got the exact same result so it has to be something with that weighted line.
I'm wondering about filling weighted line with Hydrogen peroxide, capping and then flushing out..OR...I have a 50' piece of non-weighted Vinyl line I can try and maybe verify my weighted line being the issue.. That might be the thing to try.

I have done a dead-head pressure check and it will produce 41psi.

I drilled 1/16" holes every inch around diffuser (soaker hose type-because I have another setting here), worked normal for about an hour then slowly fizzled out. New diffuser will run the same amount of time and also slows and stops.

I installed a barb on one of my air nozzles at shop. Clamped hose to nozzle and run 120psi through hose from a 90 gal compressor for several minutes at a time, let compressor catch up, do it again.. I think I need to try the hydrogen peroxide or new hose. Hope I don't need to replace weighted line every 3-4 months.

I have no knowledge of the air systems whatsoever. But it almost sounds like a vacuum leak. Like maybe not a good connection or a split in the line somewhere. Like I said I have zero knowledge on this just a thought in my head.

This is what I would try...

First, what pressure does your pump run at when you start it up under normal conditions (when it bubbles well before tapering off)?

Disconnect the diffuser line from the pump (at the pump) and rig up a short line and valve instead (maybe a softer hose and vise grips to pinch the hose in the absence of a valve). Open the valve, turn on pump, close valve just enough that you acheive the same pressure from above question and see if the air flow tapers off. If it does...your pump is warming up and lossing its abiulity to push the air through the partially closed valve.

By doing this, you are simulating the back pressure of the diffuser, line, and depth without that stuff in the equation. If the pump continues to run at that pack pressure, it's not your pump, but something very mysterious in your line or diffuser.

If the pressure does not change, but the air flow drops...the air is going somewhere else or not as much air is being sucked in. What do you have on the suction side of the pump? Filter perhaps?

On the new pump/motor, I have an external filter with about 5 times the capacity of the original pump/motor which I have crossed referenced and found it's a Honda 13hp engine filter.
Temp is a factor I'm sure but it does this during 50 deg days as well as 80 degs.
My filter is plumbed external on north side of cabinet-which is vented also.

It's starting to sound like a kink in the hose.

Can you move the pump so it's just connected to the underwater line?

My reference to warming up has more to do with a possible crack in the pump somewhere...at ambient temps the crack could be closed and not causing a problem, but once some temp is introduced (the pump starts to warm up) the crack opens up and leaks. Far fetched possibility, but it happens all the time with head cracks in water cooled gas engines all the time.

QA, it does the same thing with the new 2.3CFM pump as it does the old 1.7CFM pump.

Rusto, I can bolt pump to outside of cabinet and run wires through a hole back to controller.
Only issue is both pumps are doing the same thing even if I leave top wide open.

Take everything off and blow in the pipe. If it has a lot of resistance then you know something is in the pipe or it is kinked or squeezed shut. Cap end and put 50 to 100 PSI threw pipe, most pipe is rated for at least 100 PSI. Look for air loss or bubbles in water. Your pipe could of cracked if condensation happened in pipe going to pond, or has been driven over maybe? How long is your pipe? I have run electric fence wire thew a couple hundred feet before just make sure you bent the leading end of the wire over on itself so it has a small rounded tip.( tape end so when you pull back out it won't catch anything) That way it will jump over splices and not poke threw a soft pipe. If you have a long run of pipe you will need to dig up at shorter lengths. I don't have an air system just giving you some options..

Snipe it's possible the inner lining of the hose is becoming de-laminated and causing your blockage.
To eliminate the hose as a possibility, see if you still have pressure at the pump when flow stops, put a tee there for a pressure gauge, if you don't already have one.

To be clear, this is the only diffuser on the system?

Another possibility is the battery, it's solar right?
To eliminate the battery as a possibility, check your voltage before and after, the flow stops.

This is solar, correct, but pump is running off of MPPT controller (Panels) during daytime. I've ran it direct from my 4 batteries as well. My system is such I have a very high capacity so even on a cloudy day the panels are more than sufficient without pulling from batts.
I've pulled the vinyl out of PVC and capped, put in pond and ran with no leaks and same pressure as at pump dead-head.
Yesterday I tried to get a pressure through entire sink line rolled up nicely on bank and I'm loosing almost 15 psi through weighted line.. there's got to be a flapper inside that line.

nehunter, I've forced full shop air through line, I loose a little pressure but not much.

Snipe,
Can you verify the pressure reading at the pump when the air flow stops? Do this without the diffuser hooked up.
What you are calling a flapper, may be the inside lining of the hose coming loose and causing a blockage.
The hose line may be defective. A warranty may be in order.

The positive pressure on the pump end and no restriction on the other, is a sure way to test the hose internally.

Number 1, I was wrong on pressure. It runs about 4-4.2psi not 41 psi.
EDIT: I just found specs that say this pump should provide 35psi new, 20 psi is lower limit. I'm only getting 4psi static.
Today I received another pump and installed it-with New hose-New diffuser-New check valve.
It will not produce air deeper than maybe 2.5'.
I ordered a diaphragm kit for the second pump thinking it wouldn't hurt to have another, then I found a new pump cheaper than what I paid for the second thinking I'll eventually run 2 systems, one in my forage pond.
This is crazy.. I'm a turbine engine specialist and I can't get my damn aerator to work where it was working fine, even with all new components.. I am completely at a loss here. short of going higher tech and changing to an inverter and running AC, I don't know what else to do?????????? Going AC still doesn't fix the problem I'm not seeing, I've replaced literally everything in the system except panels and batts, but everything is good there, voltage, amps, etc, nothing has changed in readings there either.. still using 2.2 amps at 24 volts when it works AND when there is no air. Pump sound never changes..

In response to my edit above here is my findings.
This is a brand new Thomas 107CDC20/24, there are 2 reeds in the pump head on different sides of the fixture, what I found is a totally broken reed in the top position in both the old pump and the brand new pump.




I installed a new diaphragm in original pump with new reeds and both pumps are showing 38-40psi.

Finally!!
Good sleuthing, Kenny. Congrats on tracking down the demons. This was one suspenseful thread.
Persistence pays off.

I feel like we have been to the moon and back with this thread. Glad you found the pronblem! Any idea why the reeds went bad? I'd hate to see it happen again.

I am glad you found your problem!

They don't make'em like they used to!

Sounds like the manufacturer got a bad batch of reeds. And you proved that you're not going crazy. lol

The old design of the reed stop is a back-up plate with a rounded edge, the new style is a shorter nylon reed on top of Stainless reed that spreads the bend over a longer area instead of a very localized spot.

Augie: Hopefully you don't have any issues, your pump is different design if I remember correctly, but you know where mine came from. :-))

No wonder this was hard to troubleshoot-- TWO bad pumps. Very odd, but explains the symptoms. If nothing else you are now MUCH more familiar with your system and the normal pressures you should see at the pump discharge. A long and somewhat frustrating process, but knowledge and experience were gained. Odd that a new pump would have bad reeds. Congrats on figuring it out!

So far, so good here. I'm up to 6hrs/day run time with a strong boil for the duration.

I'm sure you'll be good with your pump style Augie.. I wish I was closer to REA, I'd change a few things but if nothing else I have an entire (upgraded) back up for every piece in the system.