Sprinkler Valve using another sprinkler Valve as a Pilot?

[D_Hall]

Seems to me the more valve's, twist, turns and dead air in between the pressurized pilot and the port exit the longer it will take to vent the chamber, Yes? No?

All else being equal, true.

But all else is rarely equal. Just like a main valve, a pilot valve isn't instantly open and things are happening so quickly that a slow opening pilot valve may not fully open before the main valve starts to move. Also, while a 1" sprinkler valve doesn't have the same flow as a 1" ball valve, it DOES have more flow than a 1/4" ball valve.

The faster valve's should have a shorter distance and less dead air to move, Yes? No?

Not necessarily. With enough dead space in the pilot even a tiny pilot will perform adequately once the main valve starts to move... It will just take longer for that main valve to start moving. On the one extreme, it's nice to have a gun that fires the moment you open the pilot. On the other extreme, nobody wants to wait five minutes after the pilot is opened before the gun fires. But does it really matter if it takes 0.1 s to open vs 0.01? Both are quick enough in human terms.

What's important is that the pressure in the pilot stays low enough that it doesn't seriously slow down the valve piston/diaphragm. A large pilot valve OR a large amount of dead volume in the pilot will do nicely there. BOTH? Hey, that's gold (as long as it doesn't take too long for the main valve to start opening).

[NP Carling26]

I was looking at using this as my main valve:

And this as my pilot:

However, for the main one, what is that piece of plastic on the top? Can it be removed, or does it interfere with modifying the valve?

D'oh! That's the same valve I used. The piece on the top is the flow control. Unscrew the black part. Throw the black part away. Trim the remaining stem and prep it as per previous post. Plug the solenoid port, obviously.

Forgive me for being a noob, but I read your quick written response on how you joined then together, and I'm not quite sure what you mean by "solenoid boss." Is that where the solenoid screws in?

On a side note, it feels like this would be easier if I could just find a 1 1/2 valve that's like the 3/4 valve without that flow control crap, and then just modify it following the guides in this forum for 3/4 and 1 inch valves.

[D_Hall]

Forgive me for being a noob, but I read your quick written response on how you joined then together, and I'm not quite sure what you mean by "solenoid boss." Is that where the solenoid screws in?

Well, yes, it would be a boss where the solenoid screws in. However, as I'd forgotten exactly what the valve looked like until you posted the pic, I *SHOULD* have said the flow control boss/stem.

On a side note, it feels like this would be easier if I could just find a 1 1/2 valve that's like the 3/4 valve without that flow control crap, and then just modify it following the guides in this forum for 3/4 and 1 inch valves.

It's not any harder to mod the valve you pictured than any other valve.

[MrCrowley]

I think the valve you linked and D_Hall used is better than the typical sprinkler valves because the flow stem can be used to support the second valve. My 2" sprinkler valve also had a flow control stem, albeit a much smaller one, that I tapped and threaded with 1/2" brass fittings. If the stem wasn't there, I'd have much less support for the valve and it would be much more prone to snapping off.