How to Replace a Cold-water Dip Tube and Clear Up Blocked Hot-water Faucets

My friends were certain that my hot water heater was plugged with calcium precipitate, and that I would need to purchase a new unit. Instead, the problem was a ten-dollar part that required about one-hour to replace. It's called a "Cold-Water dip-tube", and chances are good that you'll need to replace yours as well.

A cold-water dip-tube is a three-foot plastic pipe that routes cold water to the bottom of the hot-water heater. The cold water is heated, and then rises to the top of the tank, where it flows out to the house. Without that pipe, incoming cold water would immediately mix with outgoing hot water. Not very efficient.

In the mid 90's, many hot water heaters used defective plastic dip-tubes, and by 2010, they are breaking down into a fine plastic granulate. This is the first clue that your dip-tube is defective '" you'll be noticing a reduced flow through many of your hot-water faucets, caused by a build-up of these white granules. If you unscrew the screen from the end of the faucet, you can flush this plastic from the screen, and flow volume will be immediately restored '" but only for a week or so. After that, you'll again find a build-up of plastic bits. My friends and I mistook this for calcium carbonate particulates.

A shortage of hot water is another sign of a failing dip-tube. Since the water heater isn't working efficiently, the temptation is to turn up the water heater thermostat. But that doesn't solve the problem.

Even if your dip-tube isn't defective, replacing it is easy and cheap enough that it's a good start to fixing a poorly-performing hot water heater. The process is only a few steps:

1. Scope out the hardware store

2. Spray thread-release on the dip-tube fixture.

3. Turn off water to the house and power to the heater

4. Drain the tank and release the pressure

5. Remove the dip-tube

6. Buy a new dip-tube

7. Install it, re-attach cold water, then fill the tank and turn power back on.

For tools, you'll need a pipe wrench, and possibly some thread oil '" something like WD-40 or equivalent. Use a garden hose to reach between the water heater and the floor drain or utility sink. You'll also be well-advised to have several rags and buckets to clean up any water spillage.

Scope out the hardware store

Take a field-trip to your local hardware store, first to confirm that they have replacement dip-tubes, and also so you know what they look like. There are two kinds, those with threaded collars, and those without. If you don't already have a pipe wrench and thread loosener, now's a great time to buy them. If you can return the dip-tube you don't use, go ahead and buy one of each kind. Otherwise, wait until you know which one you need.

Spray thread-release on the dip-tube fixture.

If you have a gas water heater, be sure to turn off the gas, and make sure the pilot light is out. It's dangerous to spray flammable liquids around an open flame. This spray will need a chance to work into the threads. It might be a good idea to do this a couple of days in advance, and several times, if you can live without the heater being powered up.

Turn off water to the house and power to the heater

Turn off the water to the house, and isolate the water heater. If you don't, the entire house will try to drain out through your tank. To isolate your water heater, start at the pipes running into the water heater, and go backwards. Turn off the first valve you can find, both for the hot-water and cold-water lines. The valve to turn off your house water is probably in your basement. You'll know you are successful when your family starts to complain about the lack of water '" you might want to warn them before you start.

You don't want your water-heater to be trying to heat an empty tank, and you don't want to be messing around with live gas or electrical lines. Be safe, and turn off electricity to the water-heater at the fusebox. If your water-heater is gas, follow safety instructions on the water-heater for turning off gas and the pilot light. Be certain you know how to safely do this '" a basement full of natural gas is explosive.

Drain the tank and release the pressure

At the bottom of the water heater is a standard water valve. Attach a garden hose, placed the other end in the utility sink or floor drain, then open the valve. You're going to drain a lot of water from the tank, so be patient. This will help get rid of the plastic granules that are floating around the tank. On the top of the tank is a flip-valve used to release pressure '" place a bucket under the pipe that runs out of that valve, then open it.

Remove the dip-tube

Use a pipe-wrench to remove the cold-water intake from the water heater. The water in the pipe will drain all over everything. It's not much, but you'll want to be ready with rags to catch the overflow.

Now, remove the actual dip-tube. If you can't immediately pull the tube out of the fitting on the tank, then you'll need to remove the entire collar. Since you took a trip to the hardware store, you'll have a clue which one you have. If it has a steel collar, you'll need to use the wrench to remove it. Remember: righty-tighty, lefty-loosen.

If you remove a six-inch, corroded dip-tube, then you have correctly diagnosed the problem. Pat yourself on the back, and try not to knock the corroded plastic back into the tank. Be sure to show it to your family and friends so they have a chance to remark on your plumbing prowess.

If the dip-tube is in pristine condition, then you may have problems with hard water. Put the dip-tube back in place and start considering the purchase of a new water-heater.

Buy a new dip-tube

If you didn't already buy one, now's the time to return to the hardware store and do so. Bring the old one with you, the plumbing guy will be impressed.

Install it, then fill the tank and turn power back on

Run home with your new dip-tube and install it back into the water-heater. Be careful not to cross the threads if you have to use the wrench. Reconnect the cold-water intake. With the bottom tank drain valve open and the garden hose in the utility sink, SLOWLY turn the water back on, both at the water tank and at the main water inlet. If things went well, water will begin gushing into the utility sink, and NOT from the connection at the top of the tank.

Now open up the hot water lines to the house. This will drain all the water from the rest of the house '" as well as all of the plastic crud dispersed throughout your lines.

Close the valve at the bottom of the tank, then make sure the pressure relief valve at the top is open. Allow the tank to fill for a bit, then close the pressure valve. Watch for leaks, and tighten up anything that needs tightening.

This process will also cause your faucets to spray a bit of brown water when the house fills back up '" not to worry '" just let the water run until it clears. Keep an eye on the water-heater for a couple of hours to be sure nothing is leaking. You'll also need to clean any of the faucets that have residual plastic caught in them.

That should be it. You've got a new dip-tube in your heater, and no more plastic crud in your water pipes. As a result of this repair, you should notice more hot-water for long showers, and a lower utility bill. Nice work!