Plumbing oddity


New member
My plumbing system, which has been running for over 10 year, developed a funny issue. Every few minutes, I hear a very firm “pop” or “knock” sound coming from (seemingly) the feed line, near or in the plenum where both lines (return and feed) are housed in the aquarium. About 3 seconds after the pop, I see a spurt of small to fine bubbles come out of the nozzles that spray the water back into the tank. The interval between episodes isn’t the same. Sometimes it can happen in less than a minute from the last one and sometimes it take 5 minutes to occur.

My guess is air is getting into the line, but the pump is a good 15’ away and 10’ below the fish tank (plumbing goes through the floor and travels through the crawl space). Given the gap between the sound and the air bubbles, I think air must be building up somewhere in the feed line in or near the tank. Does that seem a reasonable place to start looking?


Premium Member
I assume by “feed” you’re talking about return (from pump to tank)? I think you are probably right. Calcium buildup developed over time now allows bubbles to collect in the pipe, forming a bigger bubble. When the bubble is suddenly released by water pressure, it causes the typical “water hammer” pop. I would suspect an elbow since it would be more prone to develop a bubble trap like that.