Jpsdad

Option #2 seems to be the winner. I had a new pond builder come out and he replaced the one inch vent with a 2 inch. The siphon has gone through multiple cycles and is working properly.

Still no explanation of why this became a problem 4 years after the pond filled. But I am very happy the problem is fixed and the pond seems to have recovered.

Nehunter you were also right on target

Thanks for all the input of forum posters.

[Linked Image from forums.pondboss.com]

Cliff

Last edited by Cliff76169; 06/08/20 10:13 AM.