Fill Valves are the heart of a tank-level control system (making the control panel the brain).  There are two common types of fill valves, Float, and Electronic, used in commercial building tank fill applications.  While both can be effective, the electronic float valves (and paired controls) provide extended life through even wear, improved communication with the BAS, and ease of service. 

On this Tech Talk, we are going to cover the difference between the float style and electronic style fill valves for storage tanks. So in the city of Houston we have this code requirement where you have to go through an atmospheric storage tank before you add on a pressure boosting system.

To pressurize your building, you got two options on which type of fill valves, you would use for that tank. The style that’s been around for a long time, is going to be this one 2401 float valve from Cla Val using the 100-01 Hytrol valve, base valve configuration and we’ve got this CF1C1 Pilot assembly here that is controlling the water on, and off the valve to open and close it.Now, this is a mechanical assembly you got the float hanging down in the tank and literally just like the back of a toilet, you know, the float goes up the valve is going to turn off the flow goes down the valve is going to open up and refill the tank. Problem with these style valves is it’s mounted up on top of the tank it can be difficult and even dangerous to get in and service it and it’s all mechanical in terms of how you make any adjustments, how it turns on and off and when you have two of them, there’s no way to alternate which valve is the lead valve.

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.

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.