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

Irritrol's a good choice.
Here's what I'd go with.
Both are very reliable.
Irritrol 2500
and
Irritrol 205
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The 205 is what you have now. It's been around a long time and is very reliable.
The 2500 is also reliable and also easy to rebuild.
With the 2500 you can turn the valve on manually without using the bleeder screw.
You can't go wrong with either valve.

I'm going to use Irritrol replacement valves.

since the Buckner valves were probably relabeled products of an unknown manufacturer, you would have to be very lucky to find replacement bonnets

I tried everything this weekend and I still can't get the manifold to pressurize to close the diaphragms. And there is plenty of water in the system with sufficient pressure. In fact, the lowest sprinkler on the property is a Hunter PGP and the water stream arcs out 5-6 feet. None of the 12 valves even leak at the manifold. The only thing I can think of is one of the new Buckner diaphragms does not perfectly seal, which is depressurizing the entire system. So, facing the replacement of all control valves with a model with flow control, do you have any recommendations or preferences?

Bite the bullet and install new flow-control valves. Throttle them down, and the valves will behave.

There are two manifolds, one for the front (5) and one for the back (7). Someone suggested lengthening the springs to make sure they was sufficient pressure on the diaphragms since these valves do not have flow control. Tried that today and no luck. I've changed all of the diaphragms, no leaks, and still not enough pressurization to charge the manifold. Water flows freely and I can't imagine all 12 diaphragms being bad. I did think about the extra valve to turn off the front manifold, but as you said, as long as I'm digging up the control box I may as well build a new manifold. I may try it though just in case it works. The back manifold is under a mature ash tree and roots would make digging that out a PIA. In terms of water pressure it has never been a problem in the past and I don't think it is an issue. I could take a pressure reading from the main anti-syphon regulator. What pressure should it be? Lastly, no replacement bonnets are available as they changed the bolt pattern from 4 to 6.

One more thing. How sure are you that there's enough water and pressure getting to the manifold? You said there was, how do you know that? You might change the bonnets and still have the same problem.
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Me again, you have 12 valves. Is there more than one manifold? Can you install a shut off valve to isolate some of the valves? Maybe there are shut off valves installed already.

How about installing a ball valve after a couple of the Buckner valves. Shut them off to build pressure in the manifold. This should work if you can't find new bonnets.
Then again your valves are 18 years old. If you're going to the trouble of digging it might be a good idea to just change the whole valve.

New bonnets may be a solution to look at. These valves are 18 years old, but it may work as the replacement diaphragms are still available. I'll post the solution I end up with to help others with similar issues.

You can probably get replacement bonnets for the valves that have the flow controls you need.