*PLUMBERSSTOCK EXPERT* responded:
Hi! Thank you for posting a question under our Febco 905212 Bonnet Poppet Repair Kit. In order to answer to question accurately, we would need to know if the valve is cycling while it is humming? You may post your reply here at your own convenience. We hope to hear from you soon. Thank you for visiting PlumbersStock.com. Have a wonderful day!
Not sure what is meant regarding cycling. The noise occurs when the system changes from one zone to another, normally from zone 2 rotating heads to zone 3 spray heads. Sounds like a humming vibration sound coming from the anti siphon valve and can be heard within the house
I experienced the same issue and replaced the electric valve. It had cause a loud vibrating sound throughout the plumbing in the house. The valve was not closing properly. It was not this part.