Return Line Air Bubbles

[rommulus]

In short I am looking for help on identifying potential source of air bubbles in return lines. However I think it maybe a multiple problems so I can put down exactly what I do know and hopefully the experts can fill in the blanks.

1. My pool has a standard skimmer suction I believe with two ports, one to pump suction and one to bottom drain. The first problem is there is no means to switch suctions, to bottom suck I connect a hose in the skimmer between the two ports.

2. When I run the pump just sucking the skimmer I get strong flow with a fair amount of bubbles in the return lines to the pool.
a. The suction basket view port is full and shows some slight air bubbles at top but nothing major.
b. The pump suction inline check valve shows slight air bubbles passing into pump suction.

3. When I shift to my pool vac or to the bottom drain(via a hose)

a. The level in the pump suction basket drops but still has flow and still puts out decent pressure at the return lines.
b. I tend to build up an air bubble in the filter (DE4820 by Hayward I believe) I can often full vent for up to 3-4 seconds before water comes out which seems like a lot of air the way it whistles.
c. I also notice a marked drop at the filter inlet pressure, from a rock steady 20-24# to an oscillating 10-14#.

4. I have a solar heating system on my roof which I have currently taken off-line to troubleshoot the air bubbles, I do believe that piping could be a potential source of downstream air but I have seen similar results with the suction swaps with the heater on and off. I will note that the filter pressure tends to be much more stable but I attribute that to "back-pressure" on the pump from the fluid height to the heater.

5. My pump is a WFE-6 1.5HP Purex-Triton Whisper Flow (There is no whisper in the motor), It often sounds like a jet taking off, but when on skimmer suck with no heater it quiets down, probably due to the lowered loading.
a. Pump seems awfully big for my little pond, guessing 15k-18k gallon pool, could be smaller but definitely no bigger. I think the large pump is required to overcome the vertical height to the heater but still seems big to me.

So what I think are potential issues:

1. Pump has bad seal and is sucking air.
2. Pump has worn impeller or volute which would explain lowered performance when more lift is required.
3. I have a leak on my underground piping, potentially between the skimmer and pump. Maybe an additional leak between the bottom suction and skimmer assembly.
4. I am bringing in air downstream of pump and that explains return line air..seems unlikely to me.

The air problem is huge I am getting a stream of bubbles that is clearly visible with probably a 1/2inch diameter and perhaps 4ft long plume when on the bottom suction, when on skimmer maybe 1/2 to 1/4 as long. The air bubbles are so pronounced that my vacuum cleaner will often collect air bubbles on it and become unstable or actually float off the bottom. I have to usually shake all the hoses and the vacuum at least once every 4 hours to keep it going.

Sorry for the long post but the more info the better the answer I have usually found.
Thanks in advance for the help.

[Watermom]

Any help for this poster?