Colorado weather is highly variable one year to the next, and even one week to the next. In Fort Collins, Colorado, the last frost date is May 16 and the first frost date is September 18 (using 10% as a probability that a frost will occur between these dates). This rule of thumb means that we only have about 4 months of 90% guaranteed frost free weather. This is an issue when it comes to using a sprinkler system to water your property, because you don't want pipes to freeze and burst.
For this reason, almost all homeowners have their sprinkler systems winterized in the fall - blown out with compressed air before it has a chance to freeze. There are several options available to allow homeowners to protect their system before needing to perform a full winterization procedure, thus enabling the sprinkler system to safely run for more than 4 months out of the year. This is an important advantage, since Northern Colorado's semi-arid climate and sporadic precipitation place a lot of limitations and stress on grass and plant growth. Below, I list some options for protecting your sprinkler system while extending your watering season at the same time.
Options for Protecting Your Sprinkler System During a Freeze Event
1. Turn-on After Last Frost / Blowout Before First Frost
Usually a safe option, but limits the watering season to about 4 months. Not fail safe, however, as later and earlier frosts can still occur, and it severely limits watering capability.
2. Insulate the Backflow Device
Chosen by most homeowners to gain approximately an extra month before the last frost and after the first frost. Extends the watering season to about 6 months, assuming one does a good job insulating the backflow device. However, homeowners can run into trouble when unexpected severe cold weather occurs and they can't schedule a winterization soon enough. With extreme cold, it is almost impossible to insulate sufficiently, and damage often occurs.
3. Drain the Backflow Device and Valve Manifold
Draining the backflow device and valve manifold offers excellent protection, since there is nothing above ground to freeze. However, this is only an option if the backflow and manifold are designed to be able to completely drain, and only a small fraction of backflow devices are designed to be able to do this. It's a very wise choice, however, because it doesn't cost much extra to add the necessary components to allow quick and easy draining from both sides of the backflow and from the valve manifold. EcoWise Sprinkler & Landscaping always designs systems in such a manner because it allows significant watering season extension for a negligible additional cost.
4. Self-Draining Drip System
Since the drip system is above ground, it should include automatic drain valves on all the lines. These valves close when pressurized but open when the line is no longer pressurized.
5. Full Self-Draining Sprinkler SystemThe most versatile but most expensive option is to install automatic or manual drain valves at the lowest point of every zone. Care must be taken to ensure that the lines slope evenly to the drains without significant ups and downs which could trap water. At the drain valve a gravel pit must be installed to catch the water from the line. The pit must be lined with landscape fabric to keep dirt from filling the pit and creating a hole in the yard.
Hopefully this helps your understanding of some important design considerations. Call us if you have any questions. We are happy to help!