Backyard Aquaponics
A place to discuss aquaponics

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Strange that there is no reply from the OP, re the size of the stand-pipe.. ( that I could see )

I have the same issue as my system is right outside the neighbor's bedroom..

I got a length of 4" storm water pipe and drilled a zillion holes below the GB surface , and buried it over the standpipe. (and wrapped in shade cloth to keep the tiny clay balls from entering)

You can buy both internal and external caps.. both work to keep the noise covered..
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