herbie and basement sump
 

I just setup a new tank and the sump is in the basement.

I have a gate valve about 2 feet below the overflow, a union right below it and then about another 12 feet of 1.5 inch pvc down to the sump.

i cant seem to get the overflow completely silent.

it seems like there is air coming in through the union right below the gate valve which is causing noise. I have it tightened as much as possible but still i get noise from it.

any idea on how to resolve this without removing the union?

If its air entering and no water leaking out of the union, perhaps a very, very light coat of aquarium safe silicone can seal the leak and make it more air tight. Just enough so that you can still open up the union if you need to. [I'm assuming that opening the union is not something that you will normally need to do, other than for a major plumbing project or tank tear-down]. If nothing else, it should eliminate the leaking union as a possible cause and you can check else where in your plumbing for the source of the air/noise.

you say can't get overflow silent, but where's the noise? Is it gurgling in the line below the gate valve?

With mine I placed the gate just above the sump so the drain is full of water and area around the tank is silent.

+1. Move the valve to the basement just above the sump.

but how would that work with adjusting the valve. wont making adjustments be a huge pain in the butt. always going up and down for every minor adjustment.

yes its gurgling right below the gate valve. but i sounds like really fine bubbles

and there seems to be a click/knocking sound once in a while.

couple of times up and down the stairs every 6 weeks re-adjusting after opening to flush out the snail shells not a big deal. Usually though what causes need for adjustment is filter sock dirty, swap it then don't even need to touch the valve.

Seems like I've adjusted this one 100 time so far and i can't get it right

Is it salty yet? I haven't tested this yet but I've heard that Herbies can't be tuned with freshwater.

Yup it's salty. I have it kinda quiet now. But there seems to be a gushing sound at the valve. Like water isn't going through smooth