I think that rain bird can tell you how many emitters per valve so that would answer that question

We have rain sensor and would not be w/o it. You can adjust sensitivity so during summer if you get just a little drizzle, sensor can b adjusted so that system still runs despite drizzle

Are you a homeowner or irrigation contractor?
If you are a homeowner, adding valves is probably not something you will want to do yourself. You will need to have a design plan to make sure you don't mess up the pressure or install the valves in improper places. Digging will be involved as well. After the valves are installed, you will need wiring done back to the timer as well. If these are things you are not comfortable doing yourself as a homeowner, consult an irrigation contractor. If you would be comfortable with valve installation, consult a design team or irrigaiton contractor.

And yes, a rainsensor can save you lots of money on your bill (will "pay for itself") and help you to avoid overwatering in the event of rain.

To make those changes ...

1 - add valves to the manifold in the valve box or boxes for the new circuits, or add a new box.

2 - wire in the new valves

3 - Locate the spot where you want to cap off the existing run or runs to shorten it. Cap them off.

4 - Lay pipe (if you are using emitters you can run the black tubing) to where you want the added runs. Install emitters on the black pipe.

As mentioned by others, what your suggesting is a pain in the rear lol! "zone splitting" is usually only done as a last resort... usually when someone has had a catastrophic and irreversible loss of pressure/flow, and the zone will no longer function at all even when nozzles are adjusted down to their minimum.

May I suggest an alternative? tweak your drip emmitters. they come in different flow rates and are easy and inexpensive to replace. if one area drys out faster than others, consider amending the soil to have it retain water longer.

Barring that, I'm afraid splitting a zone does involve quite a deal of digging, wiring, piping, backfilling and all other manner of pain in the butt-ness. also assuming that hunter timer is a 6 zone model, if not it will require an upgrade. I would second a professional, since theres lots of room for the inexperianced to make a mess up of a zone split.

I apologize for not being clear as I automatically assumed you were hiring somebody for the job. Def not a DIY job. We added to our system and as silverdragon said, addition is a poor choice of word--it was more like creating a new system even if part of a bigger system. In my area it wasn't prohibitive and we considered it an investment/improvement for future resale.

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