What does a water heater dip tube do?

Hot water sits at the top of the tank, and that is where your faucets draw from. Cold water has to enter somewhere, and the dip tube puts it at the bottom instead. Bradford White's service manual describes it this way: as hot water is drawn off, it is replaced with cold water delivered through the dip tube to the bottom of the tank.

A Phoenix home inspection firm defines it the same way: a pipe that routes water coming into a gas or electric water heater toward the bottom of the tank.

A. O. Smith says its self-cleaning dip tubes help reduce lime and sediment buildup and maximize hot water output. They are made from a PEX cross-linked polymer.

### Where is the dip tube, and what does it look like?

You can't see it from outside. It sits in the cold water inlet fitting on top of the tank and reaches down inside. Bradford White treats the inlet nipple and dip tube as one assembly and lists the parts to inspect: the tube itself, the hydro-jets near the bottom, and the anti-siphon hole. Rheem's parts diagram for its electric heaters shows the dip tube and a dip tube gasket as separate parts.

That means a failure happens out of sight. You find it from the symptoms, not from a look at the tank.

Look for two signs.

1. 1Lukewarm or short hot water. Bradford White lists "Damaged dip tube" among the causes of not enough hot water, next to an inoperative lower heating element and thermostats set too low. The same inspection firm says that if the tube breaks off toward the top of the tank, it "improperly allows the cold water to discharge into the top portion of the tank rapidly cooling off the hot water."
2. 2Plastic bits in faucet screens. The inspection firm says that when the dip tube fails, "faucets may become clogged with plastic pieces of the failed tube." Unscrew an aerator and look.

Neither sign proves it. A lukewarm shower can also come from a burned-out element, a low thermostat or a tank that is too small. Our page on why you run out of hot water so fast walks through those checks in order. Gritty water that could be sediment or plastic is covered on our page about sand and grit in hot water.

### How do I check for plastic pieces?

Unscrew the aerator from a hot water faucet, the small screen at the tip of the spout. Turn the hot water on with the aerator off for a moment, then look at what collected in the screen. Do the same at the kitchen and a bathroom faucet, and look at the showerhead screen too. If you see plastic pieces, the tube is likely coming apart.

If the screen holds only fine gritty specks, that may be mineral sediment instead, and the sand and grit page above covers that.

### What else causes lukewarm water, and what should I check first?

Several things can do it, so check these before you drain anything.

Bradford White's service manual says the most common cause of improper electric water heater operation can be linked to heating element failure, and that checking the elements first is a good idea when there is not enough hot water. Its list of causes for not enough hot water also includes an undersized heater, high demand, very cold inlet water, plumbing connections reversed, sediment or lime buildup on the elements, and loose wire connections.

A. O. Smith's guide adds that seasonal changes in cold water temperature and hot water usage can generate "not enough hot water" complaints, and that faulty shower controls or defective thermostatic mixing valves can cause it too. Its first step is to set both thermostats to 120˚F. Our page on testing a water heater element covers the resistance check, and A. O. Smith gives 5 to 25 ohms as a good reading.

Here's the play. Rule out the element, the thermostat setting and the shower valve first. If those all check out and the water is still lukewarm, the dip tube moves to the top of the list. Sediment on the elements is a separate problem, and our page on flushing a water heater in Phoenix covers it.

A cracked dip tube is replaced, not repaired, and the job starts with draining the tank.

### Can a cracked dip tube be repaired?

No. Bradford White says the inlet nipple and dip tube should be free of cracks and any blockage, and that damage such as cracks, restriction due to deformation or unintentional holes is not field repairable. It says the inlet nipple and dip tube must be replaced. It also says the small openings near the bottom of the tube, which it calls hydro-jets, and the anti-siphon hole approximately 6 inches from the bottom of the nipple should be open.

### What are the replacement steps?

The tube sits in the cold inlet fitting on top of the tank, so replacing it means opening the plumbing there. Bradford White's procedure for its electric models runs like this:

1. 1Turn the power off to the water heater.
2. 2Turn off the cold water supply, connect a hose to the drain spigot, open a nearby hot water faucet, and drain the heater to a point below the inlet connection nipple.
3. 3Close the spigot, disconnect the inlet nipple from the plumbing, and remove the nipple and dip tube with a wrench, taking care not to damage the threads.
4. 4Install the new part, reconnect, restore the water supply and refill the heater.
5. 5Be sure the tank is full of water before turning the power on.

Those steps are for an electric unit, so check your own heater's manual before you start on a gas one. Water heater work also means hot water and heavy fittings, so if the tank is hard to reach or you are unsure, hand it to a licensed plumber.

Heat is the trap. Rheem's manual says not to apply heat to the hot or cold water connections, and that any heat applied to the water supply fittings will permanently damage the dip tube and/or heat traps. Its instruction for sweat connections is to sweat the tubing to the adapter before fitting the adapter to the heater's water connections. That's the fix.

If the tank is old, corroded or leaking, the dip tube is the smaller problem. Our page on whether to repair or replace a water heater helps you decide, and why you might have no hot water covers the other failures to rule out first.

HQ Plumbing and Air is licensed and insured and takes emergency calls 24/7. Free estimates, and you'll get an upfront price before we start.