A.O. Smith Water Heater Dip Tube Replacement Guide — What This Part Does
The dip tube is a long plastic pipe attached to the cold water inlet at the top of your water heater. Its job is to carry incoming cold water all the way down to the bottom of the tank so the heating elements or burner can warm it efficiently. Without the tube, cold water would dump in at the top and immediately mix with the hot water on its way to your faucets.
When the tube cracks, disintegrates, or breaks apart, cold water short-circuits straight into the hot outlet near the top of the tank. You lose usable hot water volume and get lukewarm showers even though the heater is firing normally. A.O. Smith heaters manufactured between 1993 and 1997 often used defective polypropylene dip tubes that became brittle and broke down over time. Age, heat, and water chemistry also degrade the plastic in later units.
Signs It Needs Replacing
- Hot water runs out much faster than it used to Your shower turns lukewarm halfway through, even though the heater used to supply enough hot water for the whole household.
- Water feels lukewarm right from the start Cold inlet water is mixing with hot water at the top of the tank instead of being routed to the bottom for heating.
- Temperature swings at the faucet Hot water delivery is uneven or fluctuates between warm and hot during use because the stratification in the tank is broken.
- White plastic fragments in faucet aerators or showerheads Pieces of disintegrated dip tube wash through the hot-water lines and lodge in strainers and screens.
- Heater is from the mid-1990s and has never had the tube replaced Units manufactured between 1993 and 1997 are part of the industry-wide defective polypropylene dip-tube recall era.
- No improvement after flushing sediment or checking heating elements You have already ruled out thermostat settings, sediment buildup, and burner or element failures but the hot-water problem persists.
How to Replace It
- Turn off the power to the water heater at the circuit breaker if it is electric, or turn the gas control to the pilot or off position if it is gas-fired.
- Close the cold water supply valve feeding the heater and open a hot-water faucet somewhere in the house to relieve tank pressure.
- Attach a garden hose to the drain valve at the bottom of the tank and drain about 5 to 10 gallons into a bucket or floor drain to lower the water level below the cold inlet fitting.
- Use a pipe wrench or large adjustable wrench to unscrew the cold water inlet nipple or fitting at the top of the tank where the dip tube is installed, then pull the old tube straight out and inspect it for cracks, missing sections, or complete disintegration.
- Measure the height of your tank from the top to a point about 3 to 4 inches above the drain valve or thermostat, then cut your replacement dip tube to that length if it did not come pre-sized for your model.
- Wrap the threads of the cold inlet fitting or the new dip tube’s threaded connector with three to four turns of potable-water-approved PTFE tape, then insert the tube into the tank opening and hand-start the threads to avoid cross-threading.
- Tighten the cold inlet fitting snugly with a wrench, taking care not to over-torque and crack the plastic tube or damage the tank threads.
- Close the drain valve, reconnect the cold water supply, and open the valve slowly to refill the tank while leaving a hot faucet open to purge air until water flows steadily.
- Restore power at the breaker or relight the pilot and return the gas control to the on position, then check all connections for leaks and allow the heater to recover to full temperature before testing hot water delivery at fixtures.
The Part You Need
| Part | Notes |
|---|---|
| Cold water inlet dip tube assembly | Amazon | Check the model and serial number on the rating plate attached to the side of your water heater to confirm tank height and purchase the correct length tube. Many aftermarket universal tubes can be trimmed to fit your specific tank depth. |
| PTFE pipe thread tape (potable water rated) | Amazon | Use only tape or sealant approved for drinking water systems to seal the cold inlet fitting threads during reinstallation. |
Related Error Codes
If this part is failing you may also see one of these codes:
- A O Smith Water Heater E2 error code
- A O Smith Water Heater E4 error code
- A O Smith Water Heater E6 error code
When to Call a Pro
If you are uncomfortable draining and refilling the tank, working with threaded fittings under residual pressure, or if your heater is gas-fired and you are not confident relighting the pilot or verifying safe burner operation afterward, call a licensed plumber or water-heater technician. Gas appliance work carries code and safety requirements in most jurisdictions. Also call a pro if you discover heavy sediment buildup during the repair, if the cold inlet threads in the tank are damaged or corroded, or if the heater is very old and may need full replacement rather than a single-part fix. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.