Types of Enclosure Materials & Use Cases

Marine-grade aluminum is the best material built for long-term, all-weather protection

A marine-grade aluminum alloy stands up to corrosion, UV and the harsh conditions that break down lesser materials, which is why it performs across marine environments and other demanding outdoor applications. A locking mechanism protects the equipment inside from thieves, vandals and accidents, and the enclosure is built to outlast the internal components it houses.

R-9 polyisocyanurate insulation provides frost protection. A slab-mounted heater delivers freeze protection for the pipes inside the enclosure and the riser pipes beneath it, which matters anywhere freezing temperatures occur. The enclosure secures to a concrete slab and gives crews easy access for service through hinged doors and removable panels.

Size options are close to limitless. Safe-T-Cover carries ASSE certified standard models from 9" x 26" x 25" to 90" x 174" x 90", with far larger custom enclosures built to spec. Every enclosure comes in four colors at no extra cost, with additional options available for a small fee. Modular design makes each custom enclosure easy to tailor — size, color, climate control, cutouts and additions — for indoor or outdoor use.

Before aluminum and fiberglass enclosures were an option, backflow preventers were covered with some type of box or building, often made of wood, brick or block. But brick and mortar may not comply with ASSE 1060 standards.

The materials are not on ASSE's approved list, so they're not subjected to the same rigorous testing for material quality that aluminum backflow enclosures undergo. Most municipalities strongly recommend or require that every enclosure for a backflow preventer be ASSE 1060 certified. And if freeze protection matters at the site, a design engineer would need to certify that the backflow device can withstand winter conditions inside a masonry structure.

Cages for backflow preventers and other equipment come in a range of sizes, with a custom size available, and they've been on the market for decades. They're most popular in warmer climates like Southern California.

Cages have no insulation, and therefore no frost or freeze protection. They generally have a powder-coat finish over steel and a locking mechanism. They gained popularity after the 2008 housing crash, when precious-metals theft surged, and cages were marketed as the cheapest, most dependable defense against vandalism.

The problem: a cage is often secured with nothing more than a cheap lock, and because a thief can see exactly what's inside, it does less to deter theft than a solid enclosure. Cages once cost less, too. Today they run about the same price as an aluminum enclosure, and without the protection.

Manufacturers that specialize in fake rocks usually sell a mix of products meant to work together. You might find fake rocks or plastic enclosures paired with insulated bags. One company's bag uses R-13 thermal insulation to provide frost protection to the pipes inside it, but it does nothing to guard against theft or vandalism. Those bags come in a few sizes, from 24" x 24" to 60" x 60", in green, blue and tan. Because they only insulate, they're usually sold alongside a fake rock or plastic enclosure. Both are aimed at smaller equipment, typically a 2" or smaller backflow preventer.

Fake rocks are primarily an aesthetic choice. Most do not lock or provide freeze protection on their own. A recurring problem is the tapered interior: customers often discover their device will not fit inside. Measuring every part of the assembly, and knowing the dimensions throughout the entire enclosure, is the only way to get the right fit. Rocks are commonly available in varying shades of gray, tan and brown.

The best-known fiberglass enclosure manufacturer was acquired by a larger corporation within the past decade. Like Kleenex® or Coke®, the brand name often gets used in place of the general term heated enclosure. The company makes fiberglass and some aluminum enclosures with a locking mechanism for protection from thieves, vandals and accidents. Spray foam insulation provides frost protection, and a wall-mounted heater can add freeze protection for the pipes inside the box.

Standard models run from 20" x 6.5" x 22" to 83" x 26" x 55" and come in beige. Fiberglass holds up to caustic conditions, but the covers are vulnerable to fiber bloom and cracking from UV rays as the exposed glass fibers lose their UV resistance over time. The spray foam can also break off during shipping or as the years pass. Because the pieces are molded, custom sizes are harder to produce, and so are cutouts and removable panels. In larger sizes, fiberglass enclosures are comparable in price to Safe-T-Cover enclosures.