The dip tube — it has an odd sounding name, and many people aren’t aware of its existence in their water heater. But if you’ve been getting less hot water than you’d like, this little guy could possibly be the culprit.
If you’ve ever looked at a water heater, you’ll see that the cold-water inlet and hot-water outlet pipes are both located on the top of the tank. When a hot-water faucet is opened in the house, hot water sitting at the top of the tank exits through the hot-water outlet. Cold water flows into the tank to replace the hot water that’s leaving, providing both pressure to push the hot water out and a fresh supply of cold water for heating.
However, if the cold water simply entered the tank at the top, right next to the outgoing hot water, it would mix with the hot water and quickly cool it back down. To prevent that, water heaters utilize a dip tube, which is simply a long plastic tube inside the tank. It sits directly below the cold-water inlet pipe, and extends down to within a few inches of the tank’s bottom. Thanks to the dip tube, incoming cold water is directed to the very bottom of the tank, where it can push the hot water out without immediately mixing in with the hot water near the top of the tank.
Dip tube technology is not new, and it’s not complicated. However, things can occasionally go awry, as was the case with a huge number of water heaters manufactured between about 1993 and 1997. Many of these heaters had defective dip tubes, eventually leading to a class-action lawsuit. Water heaters manufactured after that time have a newer type of tube that is less likely to have problems, but they’re not always foolproof either.
If you’re not getting enough hot water, a defective dip tube could be one reason for the problem. This is especially true if your water heater was manufactured between the dates mentioned above.
First of all, look for common indicators that the dip tube might be bad. Perhaps the most obvious is a sudden shortage of hot water, even though you’ve made no other alterations in your water usage — in other words, where you might have had plenty of hot water for a shower before, now you run out quite quickly. Loss of hot-water pressure and low hot-water temperatures can also be indicators.
Another common indicator is small particles of white or gray plastic in your hot water, which could be coming from a dip tube that is broken or deteriorating. Remove the aerator from your kitchen or bathroom faucet, and if tiny particles of plastic are trapped on the screen, this is a very strong clue that the dip tube is what’s creating the problems.
REPLACING A DIP TUBE
Replacing a defective tube is typically something you can do yourself. It’s a pretty straightforward repair, requiring only some basic tools. First, shut the power to the water heater, or shut off the gas supply. Shut the incoming cold water by closing the main supply valve, which is located near the top of the water heater, above or next to the cold-water inlet. Inside the house, open the hot-water faucet closest to the water heater’s location in order to relieve some of the pressure.
With an adjustable wrench, loosen the nut holding the cold-water flex line to the top of the water heater, then lift the flex line off the pipe and swing it out of the way. The heater will be stamped with "hot" and "cold" markings next to the pipes, so you know you have the right one. Remove the fitting on the top of the tank, and pull out the dip tube.
If the tube is defective, purchase a new one at any plumbing supply retailer. Take the old tube to the store with you, along with the make and model number of the water heater.
Reverse the steps to install the new tube. Insert the tube into the tank, reinstall the fitting, then reconnect the flex line. While you’re at it, flush the tank to remove any sediment and plastic particles.
Shut the hot-water faucet in the house, turn the cold-water supply valve back on, and check all the fittings for leaks. Once you’re sure the tank has refilled completely, turn the power back on or relight the pilot light.
If you have any doubts about how to safely remove and replace the tube, how to relight the pilot light, or how to deal with any other issues concerning your water heater and a lack of hot water, contact a licensed plumbing contractor.
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