Return gurgle noises

[Spelter]

Why does my return sometimes gurgle? This is accompanied by lowering of the water level in return section of the sump. Then it stops and the return section fills and repeats. At times it does not do it for days then starts back up again.

 

I have a standpipe with an inverted elbow at waterline. The standpipe continues above waterline and is capped with a hole drilled in the cap.

 

 

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[Scott_LM]

I would check the hole drilled in the cap. It sounds like your return is siphoning. Even if partially blocked a siphon can still be created.

 

Do the days that it happens coincide with cleaning the pump?

[Coral Hind]

I agree, you need to drill out the hole a little larger in the cap. I have a hose inserted in the hole which also helps to keep the noise down.

[zygote2k]

I think it's none of the above.

I'm willing to bet that the return pump is too powerful for the overflow box. Dial back the return until theres' no surge or gurgle.

[countryboy]

When mine does it, I clean the air hole and I'm good to go

[Origami]

Frank, the most likely cause in my opinion (as many have already stated) is going to be a slightly undersized air hole (vent) in the cap. This can come out of the blue if there's salt creep plugging the existing vent or if the vent is slightly undersized. Try grabbing a drill bit the size of the existing vent or a bit larger and clearing the vent out. If you need to, you can enlarge it. If the cap is removable, I've seen designs where people drill a hole in the side of the cap and through the standpipe, so that a twist of the cap can adjust the size of the air vent (by changing the alignment of the two holes). The oversized return pump is also a possibility, but many times, when the problem surfaces in an otherwise well working system, it's a constriction on this vent.