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

This is a sprinkler system that came with my house bought in 2012 and I recently decided to test it out. It is now a big project for me and I wish I never turned it on to test it because I am absorbed by it and becoming frustrated.
I have 3 sprinkler zones running off a 3/4 HP well pump and it is separate from the home well system. The pump has a flow of 10 GPM and I confirmed this with the 5-gallon bucket test multiple times. The pump kicks on at 30 PSI and off at 50 PSI.

Zone 3 is the backyard which has just 3 rotors throwing about 50 feet that work fine and maintain a constant 40 PSI at the pump. I am happy with this zone.

Zone 2 is the front yard with 4 rotors that are supposed to throw around 25 feet each but only throw about 10 feet each. The pressure gauge (which is right off the pump) reads 0 and slowly creeps up to 10 or 15 PSI for this zone. It never goes higher. Capping off heads will result in more flow to the uncapped heads and further throws, but the PSI gauge behaves the same.

Zone 1 is the most problematic. It is both side yards and there are 9 spray heads total. These heads won't even pop up at all. The water trickles out of them. If I start capping off heads, they will get stronger and begin popping up. 3 heads seems to be the most I can have with full performance (15 foot sprays). The PSI gauge behaves the same as zone 2. It starts at 0 and creeps up to 10. It simply won't go higher.

Money is an issue for me so hiring a professional is out of the question. I have run the zones both manually with bleed screws and also with the control box. There is no difference in performance. I have determined that the valves are 100% good. Solenoids work, ports are clean, diaphragms work, flow controls are fully open.

I have searched and searched for leaks but there is nothing visible. I have capped every single head and run the zones for long periods of time with no sign of leakage. Even with every single head capped the PSI remains below 10. Why would it not build pressure at this point? I am baffled.

The control box is a Rain Bird, the valves are all Toro 254, the original spray heads were all Toro 570s and the rotors were K-Rain K1s (I've tried various heads).

I hope someone can give me some advice because I am stumped and desperate to get my lawn back in shape. It's all dug up from inspecting lines and removing heads and I don't want to mow because of all the holes and trenches I've dug so it's all overgrown and ugly and it's depressing me to be honest. I have to finish the sprinkler project so I can re-bury everything again and get it mowed.

Help appreciated!

So basically, if the water table has dropped, that would mean the two zones that are requiring more water are pumping water at a rate faster than the well is replenishing? If that is correct, one thing confuses me still: why would the problematic zones not build pressure when all their heads are capped? Could it have anything to do with the total area of pipe being used? Zone 3, the working zone, is the closest to the valves. The other 2, while they have heads nearby, travel all the way around the house and to the opposite corner. I'm just trying to understand the physics of it all in my head and why this does that. If you, or anyone, can explain a bit how the wells and pumps work in regards to this that'd be great. In the meantime I'm going to do my own research. The Maxipaws are in stock nearby so I may try them tomorrow. Thanks for the help so far.

I just tested the pressure tank because I thought it could be the problem. It's a 2 gallon tank with a pre-charge of 28 psi. I tested the psi and it was only 15 so I pumped it up to 28 again. There was no difference in the performance of the two problematic zones after that. So pressure tank is ruled out.

The possibilities at this point are: two bad leaks or a lowered water table in the ground as initially suggested by Wet Boots. Any other ideas?

I will search more for leaks, but am seriously doubting them at this point. Two different zones means two different leaks that I'm not seeing with all heads capped and running for 30 minutes on each zone. I'll keep looking though.

Yippee! I found a gushing leak! I let zone 1 run for an hour and took a walk through the zone and finally found a mushy spot. Because of time, I wasn't able to completely un-bury it and inspect it, so tomorrow I will do so, but what I discovered so far is that it is a spray head that was sunk deep and located near the street and was not attached with flex pipe but straight on the PVC. It was probably run over at some point. I am predicting I will have a similar outcome when I run zone 2 for an hour. I thought there should have been more heads!

I appreciate all the help. I'll follow up with the outcome of all this soon. I think within a couple of days I'll have a fully working sprinkler system at last!