Enclosure Vs. Pre-cast Concrete Vault: First Cost Comparison

Utility contractors are noticing that water jurisdictions across the country are changing their standards to include above-ground installation of RPZ valves. Because RPZs provide the best protection for the water supply, officials are modifying their standard backflow preventer details to eliminate the use of single and double checks to best safeguard their drinking water. If you are in a territory that historically allowed the installation of single checks or double checks in underground vaults, you may be wondering about the difference in cost between a precast concrete vault and an above-ground enclosure.

Here are the basics:

Underground Utility Vault

Standard utility vault installation today is virtually a turn-key process. Waterworks distributors and concrete casters generally provide a precast concrete vault that includes a double check or double detector check backflow preventer with all the required connections and spool pieces provided for one price. This is designed to make the purchasing and installation process easier for utility contractors.

The contractor then prepares the installation site, digs the hole for the vault to be dropped in by a boom truck, connects the spool pieces to the water line and backfills the area. The primary costs involved are (1) Preassembled Vault (2) Boom Truck, (3) Backhoe, (4) Labor.

Above-Ground Enclosure

When installing an RPZ in an above-ground enclosure, the process requires a concrete pad to support and secure the enclosure, the water line be brought above ground and attached to the double check or RPZ backflow preventer, assembling the enclosure and running an electrical line for the heater. The primary costs involved are (1) RPZ and enclosure, (2) Concrete Pad, (3) Electrical, (4) Labor.

Your Price May Vary: Above-Ground Costs Less

There are several variables to consider when analyzing the costs involved in these types of installations. Costs can vary on each aspect of the installation, especially depending on your location in the country. Rock excavation in locations like Middle Tennessee can require more to open the larger hole for the vault.

In order to compare the installation costs of vaults vs. enclosures, we reviewed multiple data points with waterworks distributors from regions across the nation. Looking at all material and labor costs, we found an RPZ in a heated enclosure is generally 10%-15% less than a preassembled vault with a double check or double detector check.

If you’re a municipal contractor in a territory requiring you to install RPZs for greater protection of the water supply, don't be discouraged! Your installation costs are probably going to decrease. If you are a civil engineer wondering if the RPZ and enclosure will cost your owner more money, now you, too, know it will likely cost less.