Water heater dip tube is the long plastic rod that runs from the top of the heater and ends few inches from the bottom of the tank. Dip tube is also another name for cold water inlet extension, as it brings the cold water to the storage tank, allowing the proper flow and heat transfer.
It is designed to keep the cold
water at the bottom of the tank as the
burner or main heating element is situated there, while separating
from hot area located at the top of the unit.
When the tap is open, pressure inside the plumbing forces
cold water into the heater tank through the dip tube. This pushes
water out of the tank toward the hot faucet.
Some manufacturers are designing dip tubes in a way to ensure better heater performance by reducing sediment deposits at the bottom of the tank and increasing turbulence.
Dip tube has to be checked regularly, and if you notice cracked or broken tube, it is time to replace it. Broken tube can affect heating operation and efficiency, as the cold water will go directly to the hot tap without being heated.
Water heater dip tube is made of polypropylene material and lower quality ones might react with the hot water and start falling apart.
The dip tube will deteriorate into chips or white sludge that sticks to the interior of the tank and plumbing while clogging faucets and reducing heaters' efficiency.
Dip tube is located at the top of the heater and it is easy to approach for repair/replacement or inspection. Follow the steps bellow for successful dip tube replacement:
Turn the power off on the heater
Close the water inlet on the main valve
Drain the cold water supply line
It is not necessary to completely drain the tank. Drain only a gallon or two to avoid accidental spilling on top of the heater.
Using a pipe wrench unscrew the pipe connector. If dip tube is attached to the steel inlet nipple, simply remove the nipple and the tube will come right out. Sometimes it is difficult to remove the nipple if the heater is old and there is heavy corrosion.
Remove the ring gasket.
Take the dip tube from inside the cold water intake hole and pull it out (you can use pliers).
Install the new tube in reverse order and don't forget to bring the rubber ring gasket back inside the connector sleeve. Apply Teflon tape to secure the connection.
Turn the heater on.
Note: Do not apply heat to the hot or cold water connections as it will permanently damage dip tube.
The problem with a conventional dip tubes is a weak water diffusing action, interference in heat transfer, lower tank capacity, part failure and its inability to make a turbulence flow and keep the system efficient.
All big heater manufacturers like AO Smith, Bradford White, Rheem are now using its patented technology to solve or reduce problem with hard water and deposits at the bottom of the tank it creates. This new design tube is few times better than standard water heater dip tube.
Bradford White for example, is using The Hydrojet dip tube, with a series of concentric "jet ports", in order to create turbulent action inside the tank. The main purpose of these specially designed and located ports on the dip tube is to redirect the water flow with the dynamic action.
AO Smith is using Dynaclean system with an innovatively designed dip tube made of long lasting PEX cross-link polymer. Rheem is using Everkleen system.
All of them are using the same way of protection and to enhance performance; when water is drawn through the dip tube, turbulent action puts dissolved minerals and lime into suspension, preventing from settling to the bottom of the tank and other elements.