PVC based sprinkler systems

PVC based irrigation system are fixed so once these are installed they can go on giving you service for many years.  many setups created in Perth during the 1970s drought are still functioning today.  Such systems are very cost effective especially for larger gardens.
 
The first step is to plan the layout to fit in with garden.  Remember its best to have different stations for lawn versus garden which means different supply lines. Draw up a list of fittings needed.  
Now to get started.  Cut the pipe to the required lengths using a hack saw, this inevitable leads to a very messy end. Deburr these rough edges with a soft cloth. Then thoroughly clean and dry the ends of the pipe and fittings before applying glue.

This glue isn't designed to to simply stick the surfaces together.  Instead it is a solvent that dissolves the PVC.  When the two surfaces, to which the solvent has been applied, are pressed together this results in a strong weld that can withstand the considerable  water pressure of our supply lines.

Apply solvent glue to both surfaces evenly. Aim for a thin film of solvent without drips.  Push firmly together and twist as you do. Hold in position for a little time to ensure it grabs and doesn't come out. Wipe excess glue off with a rag. If you do apply too much solvent it can run down the pipe forming a bead. As the solvent eats its way into the pipe it can cause a weak spot that result in a split in the pipe when high water pressure goes to work.

Don't use old glue. There is nothing worse that setting up the whole system only to have the joints fail as a result of old glue.

Allow a few hours before turning the water on

There are two main types of damage that occurs with PVC systems. First is the traumatic resulting from an event such as digging or lawn aerating with a fork.

These are quickly detected by a fountain of water rising up from the ground when the system is turned on.  

The second form of damage is not quite so dramatic and results from root pressure on pipe leading to squeezes and ruptures underground.  Cars standing above pipes can also create compression.

The first sign of an underground leak is often seen as sprinklers suddenly failing to cover properly.  Keep an eye out for areas of lawn that are bright green colour compared to the rest.

The first step is to dig up and remove the damaged section of pipe. If in a lawn cut wedges of grass and soil using a spade.  These will make it easier to replace the lawn seamlessly after the repair.  Give yourself room to make clean cuts at right angles to the length of the pipe.

As a general rule cut out the smallest length you can.  It's important that you remove any pipe that has been damaged or distorted.

If roots are the culprits it's going to be necessary to cut through these and remove the sections causing the problem. Lots of folks become concerned that this operation will severely weaken a tree.  Don't worry the total mass of roots is usually greater than all the growth above ground.  A few roots removed wont have any serious impact on the integrity of the tree. It roughly equivalent to pruning a branch above ground.

How to replace the missing pipe?  Depending on the length you may need to add a short length of pipe but even then the problem of a lack room to move the joints backward and forwards needs solving.

There are fittings designed just for this situation.  The telescopic repair coupling has a sleeve inside that allows you to bridge the gap.

The next step is a critical one - measuring the gap the fitting can fill and cutting the pipe appropriately.  Use a marker after you have lined everything up.

Its an interesting thing that long after you have filled in the irrigation trench tree roots seem to find it a happy hunting ground, not for any moisture because PVC dose not weep but most likely because of the looser soil.  So it's worth putting a bit of effort into compacting the soil when you have finished the job.