Irrigation system help request.

[Red]

I have agreed to look at, and possibly repair, a sprinkler system that has been in the ground for at least 10 years. It has also had many hands twiddling with it over those years. (One of those problems where you never know what you'll run into.)

The controller has 8 zones with 1 to 4 sprinkler heads per zone. The heads are a mix of partial circle, full circle, and rotary. Input pipe to the valves appears to be 3/4" PVC. The sprinkler heads have 1/2" threaded risers. Not yet sure what size pipe comes from the street. The controller is properly operating all 8 valves. Most all heads are Rainbird, or equivalent. I don't know how well it worked when new vs now.

The zones with up to 2 low volume heads appear to work ok. Any more than 2 heads greatly reduce the amount of water coming out of all the heads. The zone with 4 heads is not much more than 1-2' spray radius per head. The field has had a few faucets added to the supply line and the loss of volume/pressure when a zone is activated is very apparent at the faucet also.

My first impression is either loss of pressure or loss of volume. Anything else? Assuming that the whole field uses 3/4" PVC, would that provide enough volume for 4 heads at any one time? Would there be any noticeable improvement using 1" for supply?

I want to explore all reasonable possibilities before I start tearing things up. All opinions are welcomed.

Red

[hrhofmann]

How long since it has operated properly, if ever???

[Red]

"properly" is subject to interpretation, as is "close enough for government work". I'm not sure, but my guess is that it was once better than it is now.

Red

[norminn]

Wow! You've taken on a major learning experience...there is a web site with loads of info for irrigation systems and I consider it a specialty.

You should start by learning the size and pressure of the supply. Next, on zones that have poor coverage, you might want to cap off each head to get an idea of how well the rest operate. Every change in head size with affect the others on the same zone in some way. Local water demand can also supstantially affect coverage...if everyone in the neighborhood waters at 4 am, there won't be much pressure at 4 am.

Might also be a good idea to take off a head on each zone and flush the line well...sand will clog up heads.

Let us know how it goes :o)

[Oren]

If the zone valves have an adjustment screw. I would look at that for an adjustment. The valves have a rubber diaphragm and they weaken. Try adjusting.

When the faucet/spigots were added, dirt and pebbles may have gotten into the pipe. Put a temporary -- taller riser on each head location and turn the zone on and flush the line. If you see small pebbles in the pipe (riser off), siphon them out with a sacrificial turkey blaster.

Get it working first...why change to 1" supply...

Even adjust the screws on each sprinkler head for the proper throw distance. Oh, you could also have a weak sprinkler head. Do they pop up the full distance?

Report back and let us know the final results.

[ransley]

First thing I would think is a leak, leave the system on for maybe hours and look for a wet spot, when I loose pressure its always a leak. Have you checked the heads that they are open, filter is clear and no obstructions, maybe try your own new head, you need to know flow and pressure comming in and of each zone, test it. Do zone control valves go bad, maybe thats the issue. Maybe auto drains were installed inline and dont close now so pressure will always be lower on some zones, I cant imagine that inline drains would be easy to find without drawings. Its not pipe size. How long has this owner been there, how long has it not worked, how many people have tried to fix it.

[dadiOH]

Easy thing to check is the little filters in each head. Easy - and cheap - to replace to.

[trader4]

I would think 3/4" is enough for 4 heads per zone. Of course there are other variables that aren't given, like how long all the piping is and how many GPM the nozzles/heads are. Assuming they are typical home heads and are using either the shipped with nozzles or ones that aren't a lot larger, then I doubt the pipe size is the issue.

I'd start by unhooking the incoming line at the valves and seeing what kind of flow rate you get there. Since it seems to be all the heads and zones, I would suspect it's more likely something wrong with the water coming in, rather than valves, etc.

[Red]

****Update****

Got back out there this morning and did some trouble shooting. As expected, I found some real weird crap.

I checked pressure on several of the zones. All except one was 55-60 psi. The one exception was 90 psi. Yet it shuts off when closing the street valve. Must be a regulator somewhere and that one is not on it. Can't find it though.

Checked flow rate on each zone. All were 6 gpm. Sounds like 1/2" line, but at the street valve and each zone valve I'm seeing 3/4" PVC. I'm suspecting a long splice of 1/2" somewhere.

I did see 1 valve not completely closing (had soaker hose attached) and 2 heads that looked partial clogged, so I'm thinking trash in the system.

I can handle the dirty valves and heads, but the low gpm is a different matter. It definitely won't handle 4 heads on a zone. Not sure what I'm going to do about that.

Red

[ransley]

I have 8 heads on a zone of 3/4 pipe, heads are brass and put out more gpm than rainbirds.

[ransley]

If pressure is low its the valve or a leak, someone mentioned some valves can be adjusted, so I guess check them.