Research Project Information

Research Project Summary Information

Spiral Dip Tube for Water Heaters(ST7954-1)

ThermoRise, Inc.


Traditional gas and oil-fired residential water heaters incur substantial jacket and off-cycle draft losses during operation, and achieve annual efficiencies only in the range of 40 to 50 percent. Such types of water heaters are also known to suffer from severe temperature stratification and scalding problems during periods of frequent hot water usage. Such stratification results from the typical location of tank thermostat controls, above the burner, as a manufacturing cost saving measure. Small quantities of cold water in the lower portion of the tank can cause burner operation and subsequent overheating of hot water in the upper portion of the tank if insufficient time occurs between firing cycles to allow for temperature equilibrium. The overheated upper portion of the tank then contributes to increased jacket and off-cycle draft losses, which are the primary mode of energy loss in such water heaters.

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Project Description

Phase I of the project included the design, construction and initial laboratory testing of a proof-of-concept, spiral dip tube for water heaters. Phase II will include development and testing of a production model dip tube. The project will also include technology transfer and commercialization activities.


The project will benefit New York State consumers and businesses by reducing fuel consumption and scalding potential in water heaters. Economic development benefits also will be achieved through the manufacturing of a new technology by a New York State manufacturer.

Project Results

The upper half of the dip tube was made with a spiral shape to increase the length of tube in the upper portion of the tank. The dip tube was fabricated from thin-wall plastic to promote heat transfer between incoming cold water and surrounding hot water. The dip tube also had sufficient volume to allow for optimal, additional heat transfer quantities after cold water inflow has stopped. The spiral dip tube extended to the bottom of the tank and was able to regain most of the effective storage volume lost by conventional straight dip tubes, while maintaining acceptable levels of temperature stratification. Water heater storage capacity and recovery rate were increased by approximately 20 percent. This means that a water heater of small physical size could be used to accomplish the same hot water supply performance. While the spiral dip tube achieved only a 1 to 2 percent improvement in the USDOE Energy Factor test rating for a given size unit, the use of a 40 gallon water heater instead of a 50 gallon water heater, for example, could achieve real-world energy savings of up to 10 percent by means of the reduced jacket and flue losses of smaller water heaters. The spiral dip tube, if commercialized, could benefit New York State consumers and businesses by reducing fuel consumption and scalding potential in water heaters .The contractor is seeking to commercialize the spiral dip tube technology.


ThermoRise, Inc.
8253 Sugarland Dr
Manlius, NY 13104

Principle Investigator

Hemant Kale

Universities Involved


Project Type:

Product Development

Technologies Types:

Building Systems
Domestic Hot Water

NYSERDA Contact Information

Nathan Russell


R&D - Buildings Research

Contract Details

Start Date: 1/11/2010
Project Status: Active
Contract Number: ST7954-1

Last Updated: 2/27/2012