I just joined the forums here and read your posting.

Yes, it appears that you do have a leak other than at the heads. Look for "mushy" grounds along the path of the line that feeds those heads. You'll know it when you come across it! Unfortunately, you'll have to dig down to where the source it - perhaps it's virtual hole in the line, or maybe the base of one of the head where the nipple screws into the connector attached to the line.

The concept here is to start at the heads: looks for excessive moisture around them (indicates leak at the base) and then work backwards along the line al the way to the valves in the ground in the "box".

Get a good cigar, relax and enjoy the challenge. I love that!!!

That's great advice! If you still can't find it, try turning off the sprinkler heads-many have screws in the nozzles that will shut them off when turned clockwise. That will build pressure up in the line, and often force the leak to surface, make a mushy spot, or even make a rushing noise.

If you don't find a leak, you probably need to rebuild/replace the valve.

Try turning the valve on manually and if you still have low pressure then its most likely a leak but if it works great then it could be your diaphragm in the valve. You can remove it and clean inspect it and clean it to see if that helps.

Here is a link that might be useful: how_to_website

Watch for areas of green weed or grass growth, then dig there and see if there is a wet spot.

Sue