SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Well I would love to say I'm new to these problems but....I'm not. Unfortunately, this time I cannot fix it and I'm pulling my hair out trying to figure out what to do. I live in NM so after learning to cover and insulate my 765 I stopped purchasing rebuild kits about 3 years ago. The system is about 5 years old with 3 zones, zones 1 & 2 are sprinkler and zone 3 is a drip which is probably maxed out. The only thing I have done is remove a few of the drip ends around 2 of my trees to let them flow freely from the 1/4 inch feed lines that are tied into the main 3/4 inch supply lines.

Problem: When zone 3 shuts down (drip system) the 765 will start hammering repeatedly releasing bursts of water around the cap each time. The only way I can get it to stop is to shut off the supply line temporarily and turn it back on (supply shut off is placed as described in the manual). I replaced the bonnet/poppet assembly about 2 months ago when it developed a very small leak from a slight crack in the bonnet, everything else appears fine.

After reading everything I could find, I'm suspecting a pressure issue which is not allowing the check assembly to fully seat but that is where the problem comes is....other than a visual inspection of all parts...I'm lost. I'm wondering if removing the drip ends from a few of the lines is killing my pressure and not allowing the 765 to shut down properly?? I have adjusted the drip times back and forth, I have slightly closed the outlet ball valve as described on the Febco website and the problem persits. If it wasn't such a safety hazard I would remove the &^$% thing! Any suggestions are very much welcome!

Thanks in advance!!

I had the entire system installed by a landscape company about 5 years ago so I'm not real savy as to how it is setup...From what I saw, there are 3 control valves, one for each zone, zone 3's valve is tied into a 3/4 inch drip line that essentially makes a large loop around my backyard with a cap on the end. They tapped either 1/8th or 1/4 inch tubing at various locations to supply the variety of bushes and trees throughout my backyard with a flow limiter on the end. According to the installer, granted it was several years ago.., he stated that we had not exceeded the allowable drip lines to have it operate properly. Throughout the years I have added probably 6 additional drips lines but that is it. During Zone 3 operation, everything appears to be operating perfectly, that is, the flow rate appears normal. Unfortunately, I do not have the equipment to give you an exact pressure reading, but eveything appears as it did when it was first installed. I have removed 2 of the flow limiters on the 1/4 inch lines by my two trees to allow for more water flow.

The sprinkler system runs all year long and has never had an issue such as this since it was placed in operation. I noticed that it started having issues last week when I changed the zone times from 20 minutes to 35 minutes. I have subsequently tried reducing times, slightly closing ball valves etc. with no luck. This hammering seems like it want's to shake my house apart when it starts...any sugestions are very much welcome.

Lastely, I was wondering if maybe the check assembly has developed a problem?? I just hate replacing the internal parts since they are so pricey. Also, Febco says to never use grease, sealer etc. on any parts...but a grease packet accompanies the Bonnet/Poppet replacement kit?? If I end up replacing the check assembly should I get another grease packet for the o-ring on the Bonnet?