There is a growing trend across the US you'll want to know about. Water jurisdictions are requiring the installation of an RPZ instead of a double check and many are no longer allowing a backflow assembly to be installed in a subterranean utility vault.
This growing trend is increasing the demand for insulated backflow covers. The most often asked question by design engineers and water jurisdictions is: what prevents the backflow preventer from freezing?
In this blog, the two things an insulated backflow cover should have are addressed; the proper type and amount of insulation and the proper type and amount of heat required.
Insulation: Panel Design is the Way to Go
A quality backflow enclosure will have polyisocyanurate insulation, cut to the exact dimensions of each wall and roof panel. The wall panels will have R9 insulation and the roof will have R18. The roof needs to have R18 much like our homes need to have R30 in the ceiling. This reduces heat loss and lowers energy consumption of the heater.
The insulation is mechanically fastened within each panel with retainers, which means it will stay in place during the shipping, installation and over the life of the enclosure. Check out this short video to see how the insulation is installed within the panel.
Some backflow enclosure companies insulate their enclosures with spray foam, which can crack, break and pull away from the walls of a backflow enclosure. Manufacturers also have a tough time spraying the foam evenly, but with insulated panels, you have maximum freeze protection all day, every day. The image illustrates how this would look.
That’s because the R-value for polyisocyanurate insulation is the highest for rigid-board insulation at an average of 6.5 per inch. This more than meets the R-8 requirement needed to achieve ASSE 1060 certification. Plus, you’re eliminating the risk of air leaks and under-insulated areas.
So when you are evaluating a backflow enclosure, make sure it has R18 in the roof and uses rigid insulation panels and not sprayed on insulation.
How About the Heat?
What good is the insulation if you don’t have heat? A heater should be specified if temperatures ever fall below 32 degrees for more than a couple of days. This decision to install heat is often a pay-me-now-or-pay-me-later decision. We all know how crazy weather patterns have been. If a cold snap occurs and the backflow preventer does not have a heater, the RPZ could freeze and a costly repair will ensue. Not to mention the water must be shut off while repairs are being made. The occupant of the building in this situation will not be happy. We've seen this happen many times.
Two types of heaters are available: slab-mounted heaters and wall mounted heaters. And when it comes to backflow prevention assemblies, a slab-mounted heater is your best option—especially if the roof of your backflow enclosure is insulated.
A slab-mounted heater is installed on the floor of the backflow enclosure. It not only provides heat to the RPZ, but it also warms the riser pipes 16 inches beneath the slab as well. Safe-T-Cover’s patented slab-mounted heaters meet all ASSE 1060 requirements. They’ll maintain an interior temperature of 40 degrees— even with an outside temperature as low as negative 30 degrees.
Here’s an image of a slab-mounted heater being installed. You can see it’s bolted to the concrete, so it will never move out of place. They pump out as many as 2000 watts and are available in 120V or 240V. You can even fit the enclosure with power and temperature failure alarms as a precaution.
The heater offered by most backflow enclosure manufacturers is a wall-mounted heater. If your wall heater is not UL 2021 rated, it must be installed high enough (a minimum of 12 inches) on the wall to avoid contact with water that could come from the RPZ. These slab-mounted heaters are UL 2021 certified for wet/damp conditions. This is necessary for any enclosure that is not watertight.
Since heat rises, the wall-mounted heater guarantees the top of your enclosure will stay warm. But that's not important; what's important is the RPZ stays warm. Think about it: heat rises in our homes, and the same applies inside the backflow enclosure. Since the wall-mounted heater is not installed on the slab, the lower half of the enclosure will not experience maximum freeze protection. A wall-mounted heater will struggle to maintain the correct temperature for the riser pipes and the backflow preventer itself since the thermostat is installed in the heater, which is above the pipes on the wall. Watch this short video for a demonstration of the difference.
As you can see, a lot goes into keeping the RPZ safe and warm all winter long. An insulated backflow enclosure provides the peace of mind of knowing you have the freeze protection you need (plus a secure locking mechanism for vandal protection). You’ll also eliminate the risk of flooding in your building and the risk of a cross-connection. But quality insulation is a critical part to ensure your heat is being trapped and evenly distributed throughout your enclosure.
If you’re installing a backflow preventer above ground and outdoors, make sure it’s surrounded by the best insulation your money can buy. Contact us today if you’d like to talk more about the way we install our insulation. And if you’re interested in getting more information on slab-mounted heaters, watch this video to see how it works.