# Backflow Prevention for Fire Line Taps in Denver

Backflow prevention on a fire line tap installs and maintains an assembly that stops water in a fire suppression system from siphoning or being forced back into the municipal supply. Denver Sewer and Water installs these assemblies at the tap and arranges the certified testing that water authorities require to keep the connection in compliance.

- Reduced pressure zone and double check assemblies sized to the fire line's demand.
- Installation at or near the tap where the water authority requires it.
- Coordination with a certified backflow tester for initial and annual testing.
- Repair and replacement of failed or leaking backflow assemblies.
- Documentation prepared for the water authority's records.

## Why Does a Fire Line Need Its Own Backflow Assembly?

Water sitting inside a sprinkler or standpipe system for months at a time is not the same water flowing through a domestic tap. It can pick up sediment, metal from the pipe itself, or additives used in some suppression systems. A backflow assembly on the fire line tap is the barrier that keeps that water from ever reaching the drinking water main under a pressure drop or cross connection event.

Water authorities require these assemblies precisely because a fire line is a cross connection by design: it joins the potable water system to a separate piped system that is not held to drinking water standards. Testing them on a schedule confirms the check valves are still holding and have not been fouled or jammed.

- Check valves that no longer seat fully due to debris or corrosion.
- Relief valve discharge on a reduced pressure zone assembly indicating a failing check.
- An assembly sized for an older, lower fire flow demand.
- Missing or expired test documentation with the water authority.
- Freeze damage on an assembly housed in an unheated vault or enclosure.
- An assembly installed at the wrong location relative to the tap.

## How a Backflow Assembly Is Evaluated

A certified tester runs a differential pressure test on each check valve and the relief valve where present, confirming each component holds at the pressure it is rated for. Where an assembly fails, we determine whether it is a serviceable repair, such as replacing internal check seats, or whether the assembly itself needs replacement.

- Each check valve holds its rated differential pressure.
- The relief valve on a reduced pressure zone assembly opens correctly.
- Shutoff valves on either side of the assembly fully isolate it.
- The assembly is accessible for testing as required.

## How Backflow Work Is Handled on a Fire Line Tap

1. **Confirm assembly type and sizing** We confirm whether a double check or reduced pressure zone assembly is required based on the fire line's hazard classification and demand.
2. **Install at the correct location** The assembly is installed at the tap or at the point the water authority specifies, with proper support and freeze protection.
3. **Arrange certified testing** A certified backflow tester performs the required test and files results with the applicable water authority.
4. **Repair or replace as needed** Failed assemblies are repaired where the internals can be serviced, or replaced where the housing or body is no longer reliable.

## What Drives Backflow Assembly Cost on a Fire Line

Assembly size, driven by the fire line's flow demand, is the main factor, along with whether the installation is new or a replacement of an existing enclosure or vault. Accessibility matters too, since an assembly buried in a vault takes longer to service than one mounted above grade in a heated room.

Ongoing cost is mostly the recurring certified test, which is a small, predictable line item compared to what a lapsed test can cost a building if the fire line service is suspended for noncompliance.

Call (720) 935-6221 to have the existing assembly evaluated or a new one specified.

## Frequently asked questions

**Is backflow testing on a fire line required every year?**

Most water authorities in the Denver metro require annual testing of backflow assemblies on fire lines, though the exact interval is set by the authority that owns the main the tap connects to. We coordinate with the property to make sure testing happens on the schedule the authority requires.

**What is the difference between a double check assembly and a reduced pressure zone assembly?**

A double check assembly uses two independent check valves in series and is typically used where the hazard from backflow is lower. A reduced pressure zone assembly adds a relief valve between the two checks that discharges water if either check fails, giving an additional layer of protection, and is generally required where the hazard is higher.

**Can I install a backflow assembly myself?**

No. Backflow assemblies on fire lines have to be installed to the water authority's standard and are subject to inspection before they are accepted into service. The assembly also has to be tested by a certified tester once installed, so unpermitted work typically has to be redone.

**What happens if a fire line fails its backflow test?**

The water authority can require the assembly to be repaired or replaced before the fire line remains in service. Because a fire line's backflow assembly protects the wider drinking water supply, authorities do not treat a failed test as optional to address.

**Does a new fire line tap always need a backflow assembly?**

In practically every jurisdiction we work in across the Denver metro, yes. A fire line is treated as a cross connection because it joins the potable water system to a separate piped system, and backflow prevention is a standard condition of the tap being approved.

**Are you the same company as Denver Water?**

No. Denver Sewer and Water is a private, family owned and operated company, not Denver Water and not the City and County of Denver. We install and repair backflow assemblies and coordinate certified testing, but we do not set the requirements themselves, which come from the local water authority.

## Related Fire Line Tap Services

- [Fire Line Tap Services in Denver](https://www.denversewerandwater.com/fire-line-tap-services/denver-co) New taps, connections, repair, replacement, backflow, and hydrant work on private fire lines.
- [Fire Line Tap Connection](https://www.denversewerandwater.com/fire-line-tap-services/fire-line-tap-connection/denver-co) New wet taps into a live municipal main to feed a fire suppression system.
- [Fire Line Tap Repair](https://www.denversewerandwater.com/fire-line-tap-services/fire-line-tap-repair/denver-co) Repair of a leaking, failed, or non-compliant fire line tap and its valve assembly.
- [Fire Lines in Denver](https://www.denversewerandwater.com/fire-lines/denver-co) The fire suppression side of the property: line repair, replacement, and hydrant service by system type.

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Denver Sewer and Water is a privately owned, licensed and insured plumbing contractor. We are not affiliated with, endorsed by, or connected to Denver Water, the municipal water utility, or any government entity. To pay a municipal water bill or reach the public utility, visit denverwater.org.

Source: https://www.denversewerandwater.com/fire-line-tap-services/backflow-prevention/denver-co