So from left to right:
Left: Full siphon: elbow turned downwards
middle: Air line siphon, elbow turned downwards
Right: emergency with elbow turned upwards.
I agree that the full siphon valve should not be closed that much at all, it is that way because I could never get it to work the right way.
Ill explain it with pics:
My overflow weir is end to end on the inside back of the tank
I have the feeling, the way I had make the vertical slits on the overflow elbows ( see pic below), might also have to do with my failure.
After researching a lot, I found that the main full siphon slits/opening should be a little lower then the others.
If that is true, then I am not 100% sure how I am going to do it now.... A: either change the elbow( which I believe might be impossible, its probably tight and with the hood and all, its going to be a challenge) or B: Put some tape on the upper parts of the elbow slits, so that the opening is a little lower.
If I do put that tape/change that elbow.... open up the valve more.... I believe the water level in the overflow would get lower..... 2 problems...... water falling lower into the weir from the tank itself causes noise 2nd: the airsiphon line... which ideally shud be sitting just above the elbow.....will start making a LOTTTTTT of noise....
That 2nd reason... is the reason I got frustrated and I just let it ( air line) always be under water....
So when that happened, I had 2 full siphons...... water would flow out too fast...... to decrease that flow..... the valves are so closed....as you see in the first picture..... and now the emergency upturned elbow has to work.... and as I believe enough water flows through it I get some noise ( my current issue)...its not very noisy but definitely noticable.
Ive tried so many times, its not even funny.
So thats my oveflow saga.....
Id love if you or any one can help.
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So, as to your plumbing noise, which pipe is which left to right? You made a comment about noise from the third pipe, this pipe shouldn't have any flow anyway. Going from the pick above I am hoping that the pipe. On the left,the straight one is your full siphon correct? This pipe needs to have the vavle opened more. It is hard to get perfect with a ball vavle but is possible. Confirm that I am looking at things correctly and we can go from there.[/QUOTE]