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Overflow and Flood Protection for Break Tanks in Commercial Buildings

By | Flood Protection, Level

Many commercial buildings in Houston have large water storage tanks to meet city plumbing code requirements. These break tanks provide water for fire protection pumps and domestic (potable) water pumps to supply the building. A major concern with break tanks in the building is the potential for flooding due to tank overflow. This is especially critical when the tanks are in a basement level.

In order to maintain a constant water level in the break tank, float style or electronic fill valves and controls must be used. The valves open when the tank level is low, and when the tank level returns to normal they close. With either system, there is a potential for the fill valve to fail in the open position, allowing water into the tank without control.

The Houston Amendments to the Uniform Plumbing Code Table 607.7 has specific guidelines for tank overflow and vent sizing, so in the event of a valve failure, the excess water will flow through the overflow to a floor drain. Especially on a fire tank system with large fill valves, this can be up to 1,000 gallons per minute of water pouring onto the floor of the pump room. Even when properly sized, floor drains may not handle this sudden demand (trash, etc.), and water can flood the pump room.

To avoid this situation all together, Cougar USA recommends shutting off the tank water supply when a critical high level is reached. This requires a control panel, tank-level sensors and an additional valve in the tank supply piping — often called a block valve. The block valve is normally open and only closes in the event of a tank high level.

The Cougar Systems Elite Control Panel and Tank Sensors monitor the tank levels using a pressure sensor and conductivity probes. The High Level Alarm Settings are made on the touchscreen to control at what tank level the block valve will be closed.

There are two styles of valves that can be used for the block valve. The same electronic Cla-Val used for the fill valves can be configured as a block valve. This can be an effective block valve but it must be exercised regularly with water flow through scheduled preventative maintenance (PM) to ensure proper operation of the valve. Without regular PM, there is a high probability the valve will not close in the event of a tank high level due to air on the diaphragm or trash in the tubing or solenoid valve.

Cougar USA recommends the use of a motor-operated butterfly valve for a block valve. The butterfly valve’s ability to perform is substantially less affected by intermittent use because it uses an electric motor to actuate the valve rather than a hydraulic actuator. It can also easily be tested without requiring water flow, and it requires less piping space than a same-sized Cla-Val.

Tank overflow and flooding can be mitigated with a block valve and controls but, with any tank system, the Building Management System should always monitor tank levels and alarms.

For more information or a free building assessment from Cougar USA, contact us here.

Break Tank Fill Valve Types – Float Versus Electronic

By | Level, Pressure

Many commercial buildings use storage tanks for Domestic (Potable) and Fire Water Applications, especially in Houston where it is required by Houston Amendments to the Uniform Plumbing Code Section 607. As water is used in the building, an automatic system is required to replenish the water and maintain a constant level in the tank. In domestic applications, this process can repeat multiple times an hour during peak demand loads. An automatic level-control system has two main components, Fill Valves and Controls.

Float Controlled Valves (Cla-Val model 124-01) are widely used on break tanks in commercial buildings. Float valves operate on the same principle as the valves in the back of a toilet: a float attached to a rod moves up and down with the level of the water in the tank. Float valves are simple and effective, but there are drawbacks in commercial applications. Most valves are installed on the top of tanks with the float rod directly attached to the valve, making them difficult to access and maintain. Tank-water-level adjustments are also difficult because the float rod length and float position must be changed on the valve itself.

When two float valves are used, there is no alternation between valves. The lead valve (shorter float rod) will always operate first, with the lag valve going long periods without use. This combination will eventually cause failures in both valves without proper preventative maintenance. Also, these systems typically provide little or no feedback to the Building Management System.

Cougar recommends using an Electronic Solenoid Actuated Fill Valve and a Level Control Panel to avoid all of these issues. The Cla-Val Model 136-01 fill valve uses the same base valve as the 124-01, but it uses an electric solenoid valve to open and close the valve rather than a float rod. This allows the fill station design to be improved in multiple ways.

Cougar recommends using an Electronic Solenoid Actuated Fill Valve and a Level Control Panel to avoid all of these issues. The Cla-Val Model 136-01 fill valve uses the same base valve as the 124-01, but it uses an electric solenoid valve to open and close the valve rather than a float rod. This allows the fill station design to be improved in multiple ways.

First, the valves no longer need to be installed on top of the tank and can be wall- or rack-mounted down at a level that is easy to reach. Instead of a float rod, a level sensor assembly is installed on the tank to provide level feedback to the control panel.

The levels at which valves turn on and off, or levels for Low- and High-Level Alarms, can all be easily viewed and adjusted on the Control Panel Touchscreen Interface. Level adjustments require a few touches on the screen instead of a ladder and tools.

The Level Control Panel also provides automatic alternation of multiple fill valves, thereby ensuring even wear. During each fill cycle, the lead fill valve alternates between valves; however, any valve can be manually run or taken out of service if required using the Open-Close-Auto Switch on the control panel.

The Cougar Systems Level Control Panels have Tank Alarms and Level Outputs for the Building Management Systems to monitor. It is crucial that level-control systems be monitored for Low Level (loss of water) and High Level (tank overflow) alarms to prevent equipment failures and potential flooding. For more information on overflow and flood protection, see our blog post here.

Electronic Fill Valves and Level Control Systems improve the operation of the fill station, will extend the life of the valves and provide building engineers with greater visibility of their system. For more information, please contact us.

Why is a Break Tank Required in Houston for Pumping Applications?

By | Level, Pressure

Some call them House Tanks, others Break Tanks, Storage Tanks or Buffer Tanks. If you have been in the pump room of a building in Houston, you’ve seen these large water tanks, but why are they used? The Houston Amendments to the Uniform Plumbing Code Section 607 states that upstream from a pump system, an atmospheric storage tank with an air gap between the tank and city water supply must be used. This applies any time the city water pressure is insufficient to supply a building for both Domestic (potable) and Fire Water applications and the addition of pumps is required.

The City of Houston is one of a few municipalities across the country with this requirement for both Domestic and Fire Water Pumps. The tank air gap effectively separates the building’s water supply and consumption from the city water lines. This should stop any contamination from a building getting back into the city supply and affecting others. Also, large sudden demands in a building (i.e., fire pumps) shouldn’t affect the water supply to those around it.

While a tank is an effective backflow prevention method, it does add some complications. Tank size and design, water-level controls, pump pressure design calculations and system maintenance all must be considered when using a storage tank.

The National Fire Protection Association (NFPA) Standard 22 has requirements or Fire Water Storage tank sizes. However, there is no minimum tank size for domestic water. There are multiple options for tank construction. Steel tanks with coatings for potable water are widely used, but over time maintenance on steel tanks and coatings can be expensive and time-consuming. Alternatives to steel are fiberglass and plastic, both of which carry NSF61 ratings without the need for coatings. The modular design of the FTC FRP Tank is ideal for tight space requirements of most pump rooms.

In order to maintain a constant water level in the storage tank, fill valves and controls must be used. A simple method is to use a Float Valve on top of the tank. For more control, electronic valves and a control panel are used. A quality level-control system can prevent tank overflows and flooding or dry tanks and the building losing water. It is crucial that the building management system monitor the level-control alarms for potential issues.

When using an atmospheric storage tank, the city supply pressure cannot be used in the booster pump pressure calculations; this is referred to as Flooded Suction as opposed to Pressurized Suction. Pump selections must also consider the low Net Positive Suction Head provided by the atmospheric tank. The Grundfos CR Multi-Stage Pump is an ideal selection for Flooded Suction pressure-boosting applications.

Cougar USA has worked in hundreds of buildings in Houston with storage tanks, level controls and booster systems. For more information or a free building assessment, contact us here.