I still do that because of cost (and it all passes inspection lol) Drains, bring in a friend for that because of certain codes)
There is already an app that can be used for irrigation. It's called 'Switch Scheduler and More' It's pretty easy to set up once you get your head around it. You can also add isolating sections whne there is a rain trigger. There's also the option to not isolalate all sections if they all aren't effected by rain.
I'm trying to integrate a water flow valve so I can count how many litres are flowing onto the grass & garden. Can anyone help with that? It is a 3 wire valve. 24v, Common & trigger
I am an incurable DIY person as well. I tend to spend on premium supplies when I do things though. My rationale is I am saving a fortune not needing tradesmen to do things for me so I don't skimp on supplies and required tools. In this example I wouldn't blink about buying 24VAC valves and a bunch of PVC fittings to build up a manifold for all the zones. For control I would use some sort of dry contact relay either ZWave or Zigbee, but a commercial device like a ZEN58 or one of the zigbee 4 channel units. I'd put in a hose bib(s) for winterizing and draining. Then I'd come up with amounting scheme out of the way but accessible for maintenance.
Interesting, I like it. Is there a driver for the konnected boards? Do they present as just 8 switches? or did you do your own hubduino app?
I couldn't find any 8 channel Zigbee boards, but I did find this thing on Ebay
It is Tuya Zigbee based, so I have a feeling it would work with the Generic Zigbee Multi-Endpoint switch driver and create 24 child devices. Though I have my own driver for those boards now that will allow direct access to the relays from a single parent device.
Edit: I didn't notice they have no Zigbee versions in stock 
Edit2: Ali has them for $50.
Ali also has the 12 Relay boards:
And they have the 8 channel boards:
I just bought the 12 channel from Ali. $27.65 total with shipping. I may want more than four irrigation circuits, and I would like to keep it all in one driver if I add-on. This leaves me options to add more valves.
I only wanted the 8-channel, but there seems to be no 7-24V Zigbee in stock for those.
I use konnected boards. The konnected boards I have are 6, plus they have a 'Alarm/Out' which can be used as a switch. They have changed their range a bit of late, so it couuld be more connections. Nate from konnected is very helpful if you make contact.
Of course, the 12v 8-channel board became available after I bought the 12 channel board. I now have one of these on order. I'm not sure if I can find another use for the 12-channel board, so I will probably return it.
So far I have purchased eight of the valves:
Pex to Garden hose Adapter
100 feet of 1/2" flexible irrigation hose
A bunch of 1/2" Pex clamp rings to make the valve assembly
Some 1/2" Pex Tees for the valve assembly
8 conductor wire from relay board to valve assembly
and some female spade connectors to attach the wires to the valves
I have tons of these mini-sprinklers and 1/4" tubing already
Those mini-sprinklers are adjustable 0-30 psi. My issue with these in the past was putting too many on a zone circuit causes them to drip, instead of sprinkle. Dripping doesn't cut it in an outdoor garden for coverage. I want to give them about 5psi each, to create a sprinkle area of about a square foot. I need to do some tests, but that should be about 20 sprinklers per zone, so a zone of 20 sprinklers will cover about 10 sq/ft of garden, based on overlapping them 6" and my water pressure. That is why each zone will water at a different times, to give full water pressure to each zone to get enough sprinkler range to really wet all the soil.
I have written a custom board driver that creates valve child devices, instead of switch devices.
I have written most of my new Irrigation Scheduler App and started testing it. It controls eight zones, with up to two schedules per zone, to water for a set time for each schedule. It uses my Ecowitt Rain Meter to delay or cancel the watering schedules based on how much rain we have for the day and last hour.
My old app would base watering on soil moisture sensors for each garden. I found that does not work very well outdoor gardens, as they drain out to quickly compared to pots (where sensor driven waterings work pretty well).
Instead of a soil moisture sensor in each zone, I am going to use the built-in Average Humidity app to combine my sensors into one average device, and put the sensors in a few key locations. The app will use average moisture to determine if an "emergency" watering is needed, watering all zones based on soil moisture average going too low. This would be for a hot dry day where the gardens really need a watering before the next schedule.
I may also use average soil moisture to cancel a watering, if it is high enough, which will probably be needed in case there is an emergency watering shortly before the next schedule starts, so it doesn't double water.
The scheduling app will control the valve board children, or any other smart valve, for that matter, if using individual smart valves instead.
I was going to make a single driver for the board, and have the board control endpoints without creating child valves, but since I still want to mix in a couple regular smart valves, I decided to have the app control any valve device used for each zone.
The app also creates a child data device, to set status attributes to display the zone schedules, and zone status, to be put on a dashboard. It is also a button controller to add pushable buttons to the dashboard to manually water a zone. It also has commands to set the rain delay hours and thresholds in the app.
This is the schedule input in the app below. Two schedules per zone is WAF, she wanted to water in the morning and evenings last year... though she just told me today she thinks this year she only wants to water once per day. Doh! That's Ok, we can just use one schedule per zone as the app is set-up.
Progress... I have the valve manifold mostly built. Just waiting on hose clamps to come today for the valve connections (I don't want to crimp ring those since I want them to be replaceable). Also some screws to screw down the valves to the pressure treated 2x4.
I also got the 12-channel relay board working with an AI driver, turning it into a controller that creates 12 valve children.
I'm still looking to use the eight channel board that comes this week though.
I have finished writing and testing the controller app and data driver. I will post it the code at some point:
App controls up to 10 Zones:
1, Schedule two daily/weekly watering schedules per zone, based on any day combination
2. Schedule a timer watering, every X hours for T time between set hours. For shallow crops that need to stay moist, not get a deep watering. It can also be used for every other day waterings.
3. Works with a water meter to delay or cancel the watering, depending how much rain we are getting in the last hour, or total rain for the day. Uses rainDaily and rainHourly.
4. Emergency waterings: Trigger an emergency watering of selected zones when a moisture sensor falls below a setpoint.
Preview:
Edit: No AI was used to write the app and driver. It was very handy for the board driver, however. 
Nice looking work.
No clamp needed on valve input Pex pipe? Or is it a sharp barb fitting?
I mentioned the worm gear hose clamps come today for the valve inputs, so they are not forever clamped. They will also be used on the valve outputs.
The input to the manifold itself is just a male hose connector.
I also bought some valves that will go in-line on the 1/2" tubing at the gardens, to set the pressure for the proper level of sprinkling. There will be a max number of sprinklers for each zone for pressure, but any zone that uses less than the max number of sprinklers will need to have pressure adjusted down.
I'm going to connect the wires to the relay board the correct way for this project, so I also bought a Ferrule crimp set, instead of just pushing wires into the board relay terminals.
I love my Ferrule crimper. After getting it last year I was going around the house just looking for wires I could use it on.
The manifold looks great. Nice work.
More Progress. The valves are in place, and there is hose going out to all the zones.
I realized that I had not bought enough vinyl hose for all the runs, and PEX is half the price, so I did the initial runs out behind the greenhouse with PEX. It keeps it very neat compared to hoses coming up to the valves. It goes to vinyl for the last leg of each run to the zones.
The board is now in the greenhouse on the swamp cooler. The 8 relay board finally came and it was defective, so back to Ali with that one. I decided to make use of the extra relays on the board to control greenhouse stuff by adding outlet dongles. Now I have three spare Zigbee plugs too that are not needed in the greenhouse.
I needed a box that the board would fit in, and this was just the right size.
I've put some time into the Gardens Scheduler App. It now uses dynamic zones, so the number of zones can be changed at any time, and only uses and display data for the number of zones needed. It also is doing predictive rain for delay/cancel of individual schedules using Open Weather Alerts Driver. It also tracks rain history from an Ecowitt rain meter for three days, and it uses that to determine if a watering should be skipped or delayed. Look ahead and look back for rain is based on the zone watering frequency derived from the individual schedules at the time the schedule fires.
The Gardens Dashboard is coming along as well, all displayed using the html attributes in the child data display driver.
I have some of my garden zones active with the mini sprinklers now, and I should be able to finish this up this weekend.
You probably don't care but most pex needs to stay out of uv light.
The Hubitat box is cute but not exactly NEC compliant (open air line side connections). You should probably put the gear in a steel box and ground it since there are line connections within. Strain relief or wire clamps on all line voltage cables in/out. You typically cannot comingle LV and HV wiring in the same cavity unless the LV wire is rated 600V insulation (just thicker plastic jacket on wire) but that might be getting into the weeds a bit. You probably want all this gear fed from a GFCI protected circuit as well.
Looks like lot of work getting here, your plants hopefully appreciate it!
I completely agree, but I am unconcerned about any of that. This is not in my house, where I do stay compliant. The box is fed from a plug, so it is more of a home-made appliance then actual wiring. It would be a bit of a loss if the greenhouse burned down (I guess it would melt), but I feel the chances of that are slim. The box is on top of the swamp cooler, if it melted through the top of that it would fall into 6 gallons of water below. The greenhouse itself is plugged into the outdoor GFI outlet. This is also only up and running a few months a year.
Where the PEX runs is in constant shade from the greenhouse (picture is the north side of greenhouse.) The black vinyl hose running through the gardens is going to get most of the sun.
Still, the blue is a bit bright, and I have thought about spraying it black. My biggest concern is algae growth in the pipes.
It can get brittle and break in a year.
i second rachio i have them in two houses.. no issues other that gettng the app working again after having disabled everything for the winter.