Pressure relief valve?

[wishIwereAnExpert]

So, I bought the misting pump recommended by many DIYers, a shurflo demand diaphragm pump. Well, I've only got it running 20 nozzles right now, and with its flow at 100 PSI, it oscillates on and off to accomodate the flow limitation of the nozzles.

So, what I'm looking to do is tee off the output piping, and put this bypass back into the imput. What I'm lost on is what type of valve to use. I'm looking for something that wouldn't let any water through under 90 or so PSI, but when it hit that mark, it would let a good amount through. Kind of like the safety valves on backpacking espresso machines.

Mike, have at it.

-Solly

[dragonfrog]

May I ask where you got your Shur flo? and how much?

[wishIwereAnExpert]

Got it off ebay. Was new, and that's I'll I care about. $60. Not the best deal, but I was impatient and bid on the first one I saw.

-Solly

[defaced]

Mike, have at it.

That gave me a good chuckle

The easiest way to do IMO, is to skip a pressure valve, and just use a ball valve, and tune the ouput of the pump to be less than 90 psi so the pump stays on all the time. With the ball valve full off, you've got the same thing you do now. As you open the ball valve, more water will flow which will drop the pressue. Keep opening it until the pump stays on, and presto, a simple way of solving your problem. An added bonus to this is that if your pump and water supply are below your lowest nozzle, you won't have any dripping or spraying after the pump goes off because there will be a rapid drop in the system's pressure.

You could also just snip the wires to the bypass muchanism on the front of you pump and rewire them to keep the pump on. This would essentially turn your demand pump into a bypass pump. I'm going to guess on this one, but if you cut them, and connect to two leads that go into the back of the pump, it'll stay on all the time.

[wishIwereAnExpert]

If I go the manual path, do you think a gate valve would be a better option? I'm worried about the lack of precision with a ball valve.... :?

-Solly [/i]

[defaced]

Yes, that will be better. You'll be able to tune it with more precision.

One more thing, how ever you plan to do this, take your bypass all the way back to your resivoir. This will avoid turbulent flowing water from entering your pump, which just makes noise, and also any problems that could arise when you try to start your pump. I'll post up a drawing some time today. It'll make sense with a picture.

[wishIwereAnExpert]

It makes sense now. Don't waste your time.

-Solly