Sump-overflow Works Great, Doesn't Loose Prime, But Get Bubbles In Wet/dry Pump

[1611mac]

Someone please help me understand this....

I built this

and it works great. To ensure I don't loose prime I added a Toms wet/dry pump as suggested at 4:45 in the video. (see screen shot below)

With the dry/wet pump off the overflow works great, makes NO noise, and repeated testing has shown that it restarts fine if power goes off. I'm running relatively low volume as this is a 10 gallon sump for a 29 gallon tank so I'm using 1/2 inch pvc with a 1-1/4 inch weir.

The Issue: When I use the wet/dry pump to ensure that no air remains in the overflow the pump pulls lot's of air. My setup looks just like in the video at the 5:00 mark. Again, I know that no air is entering as testing shows that the overflow restarts every time after power loss. Yet, I see lot's of air being pulled out continuously by the wet/dry pump. This makes no sense to me as if all this air were really in the high point of the overflow I'd be losing my "syphon" when the power goes off.

Why am I seeing so much air being pulled out by the pump? If so, why am I not losing prime (syphon).

Comments, Suggestions, Ideas please???? (see attached screen shot)

 

[Culprit]

Where is the pump in the sump? Could it be the water level is partially below the intake of the return pump? For instance the return pump is too high so its sucking air as well?

 

[1611mac]

Hello, thanks for the reply. Return pump in sump is on bottom of 10 gallon tank and tank is 3/4 full. And that would have no bearing anyway as the air bubbles are in the web/dry pump intake (from overflow pipe) and has nothing to do with the sump return pump. But I appreciate the reply.

 

[ounderfla69]

Its possible there is a leak in the tom's pump itself as it is running. Do you a a one way valve in the tubing between the pump and the overflow? If you do I would try and remove it and see if air gets into the overflow.

 

[1611mac]

Thanks for the reply... no... you can see air bubbles coming right out of top of overflow tube before it even gets to Toms pump. Oddly, if I unplug the Toms wet/dry pump and also kill the return pump in the sump, wait a minute, then restart everything it runs without any air in line (So my overflow is not losing prime!) I'm almost tempted to build one out of clear tubing so I can see exactly what is happening!

 

[ounderfla69]

The only thing I think it could be is that the overflow isn't flowing enough water and some air is entering the system but as long as you have that pump removing the air you should be fine.

 

[1611mac]

Yes.. I'm thinking making the overflow outlet higher. If I'm thinking right that should retain more (deeper) water in the weir and help eliminate air bubbles.