How to Design a Hot Water Tank

Hot water storage tanks dot the skyline.

Hot water is often in short supply at hotels and homes during certain hours. One method of solving the shortage is to install an auxiliary hot water tank that holds extra hot water for use when the water heater has exhausted its capacity. These tanks do not heat the water but hold the water at a high temperature until needed. A proper design for a hot water tank depends on how much water you need to store and how much money you want to spend on materials.

Instructions

1. Find the capacity of your hot water heater. The label on the heater tank will normally state the capacity and energy usage of the heater. In the United States, this value expresses the capacity in gallons.

2. Determine the quantity of hot water you require during peak demand hours. Figure out how big of a hot water holding tank you need to meet the requirements. In designing the tank, pad the maximum size you calculate by approximately 20 percent.

3. Calculate the dimensions of the hot water holding tank to meet your desired quantity of hot water. For example, if you need 200 gallons of hot water during peak demand and your hot water heater has only a 150 gallon capacity, you will need a hot water tank that can hold 90 gallons of hot water (200 gallons plus 20 percent (40 gallons) minus 150 gallons in hot water heater). Hot water tanks are generally available in cylindrical shapes. For 90 gallons you would require a tank that measures 24 inches in diameter and 50 inches tall.

4. Specify the type of lining you require for your application. There are many types of lining available for the tank including epoxy, glass, cement and galvanized. Each type of lining has limitations and benefits. The epoxy lining is by far the least expensive but tends to degrade at temperatures above 180 degrees F. Cement linings are more fragile than others but are more easily repaired when damaged of eroding. Galvanized lining is the most common in smaller tanks.

5. Select the insulation for the tank to provide the best energy efficiency. The two most popular methods of insulation are polyurethane foam and aluminum jacket insulation. While the polyurethane foam insulation provides an R-16 insulation value, it will accept most other commercially available insulation materials to increase this value. The aluminum jacket insulation incorporates an aluminum jacket around a layer of fiberglass filaments.

References

• Roy E. Hansen Jr. Mfg.: Water Tanks