The hot water tank dip tube is a plastic tube (usually whitish) inside the hot water tank. It directs incoming cold water to the bottom of the tank. People find it necessary to close the cold water valve completely for hot water before it is only warm. Replace the dip tube.
When a dip tube breaks, cold water entering the tank mixes with hot water in the middle instead of being sent to the bottom, and cools the top water. Since the hot water is drawn off the top of the tank, the water becomes lukewarm immediately.
Replacing the dip tube can be easy or it can be a catastrophe.
To replace a dip tube first shut off the water and gas supply lines to the tank. Drain several gallons of water from the tank and disconnect just the cold water supply into the tank. There should be a union fitting in the pipe to remove the cold water supply to the tank. Remove the pipe from the tank and check for any remnants of plastic in the hole.
Then install a new dip tube and reassemble the plumbing. Trim the new dip tube about six inches from the bottom of the tank. Sounds easy, eh? It can be if you have the tools and nothing goes wrong.
What could go wrong you might ask?
The pipe nipple at the top of the tank could crush or break off flush when you try to remove it.
The union might leak when reassembled.
The plumbing above the tank could leak once disturbed because old galvanized pipes are fragile and subject to leaking when moved.
Pieces of the dip tube in the bottom of the tank could disperse small pieces of plastic throughout the plumbing system. The plastic pieces can clog aerators, ruin faucet cartridges and cause toilets to run.
For most people this job is best left to a plumber. The above problems are not meant to discourage you from doing this repair. Dip tubes are replaced everyday and related problems are routinely solved. If you prepare for the worst, you will not slash your wrists if things go wrong.
Keep in mind:
Is your tank eight years old or older? An eight-year old tank is close to the end of its life.
Are you experienced at plumbing repairs?
Be prepared for the cost of a new tank if any major problems arise.
Tip 1: The layer of rust in your hot water heater may insulate the burner from the water. Once a year you should remove this rust by draining the water from the tank. This simple maintenance will save you money and prolong the life of your tank.
Tip 2: If after draining water out of the hot water tank the drain valve drips, get a hose cap and screw it on the valve. A simple fix.