Cracked Exterior Pipe

[rogman49]

Hi All,

I have a Hunter sprinkler system. The outside pipe above the backflow valve is pvc. Every year a small section bulges and cracks. The repairman who fixed the first time said the 1/4 turn ball shutoff valve inside might be leaking. After the second time it cracked I cut the pipe out myself. There was no moisture inside. The shutoff valve is not leaking. I am assuming the crack is caused by water getting in somehow. I have system winterized every year. Could there be a problem with the backflow valve? Thanks!

 

[Verdeboy]

If this happens after winterizing, then that pipe is filled with water.

Here's something I got right off the Hunter website:

Last Step In Winterizing:
The most common backflow device installed is called a Pressure Vacuum Breaker, which has isolation valves and test cocks. Open and close the isolation valves on the backflow device numerous times to ensure that any trapped water has escaped from the upper areas. Leave the isolation valves open at a 45° angle (approximately 1/2 open) and open the test cocks.

Pressure Vacuum Breaker

1. PVB Test Cocks
2. Isolation Ball Valve Inlet
3. Isolation Ball Valve Outlet

 

[Sponsor]

 

[Mr_Pike]

Do you mean above, as in upstream from the Back Flow? Or physically above like as in above the elevation of the BF?

You should have a main shutoff ball valve T'd off of your water supply, followed by another valve inside the structure that you can open to drain the remaining water from the supply side of the BF to the shutoff. I leave this valve open in most non finished basements for that very reason. I don't want a leaky main valve re filling the supply pipe.

You then open both test port valves on the side of the BF and let the water drain out of the open drain valve in the basement into a bucket.

On every system I have ever installed, there is a boiler valve T'd into the down pipe before entering ground before the valve box. You close the valves on the BF charge the system with idle air (40) lbs and open the valves until the water clears and the heads blow a fine mist. Move to the next valve until the system is complete, then I do all the zones again to catch any water that might have pooled in a low spot. You should not let any rotor zones run completely mist free very long, or you can actually over heat and ruin the gears inside. As you open the last zone on the second go around, kill the air compressor, and let the pressure equalize before removing the air source.

I leave all the drain valves open, but some others do not.
I would rather have a drip where it can be noticed, than a freeze break that destroys a BF or supply line.
It sounds like you have either a problem with slope, or with the winterization procedure. Somewhere, water is staying in your pipes. Is your drain valve inside lower than you BF preventer?

 

[rogman49]

Hi Mister Pike,

My backflow pipe looks nothing like the one pictured. There are no drain cocks on it. The plug that is removed during winterization is above the backflow valve......about 6 inches.

 

[Mr_Pike]

A picture is going to be worth 1000 words here I think. If you can get one of your situation, we should be able to tell you whats going on.

You might have an older version of a BackFlow preventer like an atmospheric or something else. This would not let any water drain from it. Maybe that plug is not so much a drain plug, as it is a port to connect the air compressor. That would push all the water through the Back flow and clear that pipe.

 

[rogman49]

Hi Mr Pike,

Thank you for the response again. I must have unusual backflow device. Looks nothing like picture #2. It is copper. There is a opening on top that the threaded plastic pvc pipes goes into. The backflow is at ground level. The pvc pipe is actually 5 pieces total. The top of the pvc pipe goes into the 3/4 copper water line and into the house. One of the pvc pieces has a plug which is removed during the winterization process. At the bottom of the backflow pipe there as a pvc piece which is buried in the ground and eventually connects to the valves. The backflow device has no drain devices or plugs of any kind. The pvc section right above the backflow is where the crack occurs. After the winterization is done in October, I was thinking about removing pvc plug again and shooting in some antifreeze.