In residential gas and electric water heaters, one important part you’ll hear about is a dip tube. It may not sound like the smartest piece of plumbing, but it’s a fact that your hot water won’t work well or last long without it.
Simply put, the dip tube for a water heater is a plastic pipe that delivers incoming tap water to the bottom of your water heater tank.
Why does a water tank dip rod go all the way to the bottom?
In a gas water heater, it’s where your heating source is, known as a combustion chamber.
This is a great spot to start raising the temperature of your water. This is because the hot water that’s leaving your tank to the rest of your house goes out the top.
So it makes sense that we need to push cold water down to get heat, then let it rise up and out the top for maximum efficiency.
Think about a lava lamp. As the attractive wax substance inside heats up, it moves to the top where it seeks to escape.
Conversely, cooler wax drops naturally back to the bottom to become heated again. Just like the incoming cold water does using a hot water heater dip tube.
Water Heater Dip Tubes and Their Parts
From what we learned above, we know that dip tubes must be long enough to reach from the top of a water heater to the bottom of the inside of your water heater tank.
But they are more than just a long, thin white tube.
In fact, it has a couple of characteristics that make it perform it’s job well and aid in how your water heater works to its fullest potential.
Near the top of your dip tube, about 6″ from its connection point is a little hole.
It’s about 1/8″ in diameter. It’s called an “anti-siphon hole”.
It’s purpose is to prevent water heater’s storage water from going back up the dip tube and out of your water heater.
There is a big debate on whether a dip tube should be called an “anti-siphon” device or not in it’s water heating application.
The truth is, because it’s an open pipe inside your tank it has the potential to let water run back out the way it came back in should water pressure decrease too much.
Does it work?
Some plumbers will say it’s not large enough to do it’s job. Sometimes with the water off, water is siphoned out anyway despite the anti-siphon hole being there.
But if you made it any larger there could be a diluting effect of cold water mixing with hot.
Others will agree that it works just fine and does what it’s supposed to.
There are water heater types that have water supplied at the bottom of the tank, thus don’t require a dip tube at all – making the siphoning issue a moot point.
When installing a new or replacement dip tube, you will certainly notice this hole.
One question you might have is what direction to face this hole as you insert the dip tube.
The answer is…
It makes no difference. It can do it job pointed in any direction.
Whew, at least one element in DIY plumbing that you don’t have to worry about.
Slots on Bottom of the Dip Tube
At the bottom of the dip tube, the last foot or so, are a series of little cut-out slots.
They are there by design to create turbulence as cold water comes in.
So instead of the dip tube delivering a clean stream of water, like from a hose, it can release inside your tank in an uneven spray.
This helps keep water moving and stirred up, aiding in the prevention of sediment settling on the bottom of the tank.
The stuff will stay suspended in the water as it grows over time.
If the mineral deposits settle too much below, you lose the efficiency of your gas chamber to heat the water.
This is something you will surely notice when you start losing hot water in your house.
Dip Tube Replacement
In most cases your dip tube will last as long as your water heater will.
There was an issue in the early to mid ‘9os where one popular manufacturer of these devices produced defective units.
What happened was over time the tubes would deteriorate into countless pieces of small white plastic.
Homeowners would then find these plastic chunks clogging faucets and shower heads.
They would unscrew aerators and nozzles only to find tiny little plastic particles accumulated in there, caught by the screen and faucet mechanism.
Once this happens, it’s most likely time to replace your water heater.
There is just not way to retrieve a broken up dip tube inside a water heater tank.
Some people have faced issues with these plastic tubes melting.
When this occurs, it means the water in your tank got too hot. It stands to reason that there are larger issues going on in that case that need to be address.
So there you have it. A quick run down on what a dip tube for a water heater is.
Most of the time, you won’t need to worry about this device. They cost about $5, but should last a while as they tend to hold up and don’t become brittle.
They also hold up to the extreme temperatures pretty well, so they can do their job of delivering cold water to your water heater tank.