How To Tell Which Water Line Is Hot and Cold On Water Heater

How to tell which water line is hot and cold on water heater can be confusing when you have no idea about it. But rest assured, it is not a difficult thing to discover.

Usually, the lines are labeled with the “C” or “H” on or above them to be identified easily. But there are other alternatives to locate.

For cold water, line check for a knob connected to it, and as for hot water line, it can be spotted as nothing is connected to it and can be spotted on end.

How To Tell Which Water Line Is Hot and Cold On Water Heater

A Complete On How To Tell Which Water Line Is Hot and Cold On Water Heater

It is important to be able to tell the difference between a hot and cold water line in order to prevent potential burns or scalds.

In order to identify whether the water coming from the tap is hot, place your hand against it for a few seconds. If it feels warmer than average, then it is likely that it is the cold water line.

If you are not sure which line is which, there are usually two valves next to each other for hot and cold water on the water heater. Open up each valve at one time and feel or look at them both. The one with steam coming out of it will be the hot water, while the other will be cold.

Problems Regarding The Waterline

Before discussing the other alternative way of identifying, it will be good to have an idea. About the problems, you may face if the waterline. 

Tying Up the Hot Water Tank Backwards

This problem may occur as you cannot distinguish between the two lines. If things like this happen, then it will be a massive problem. The hot water you are supposed to get will cool down.

The reason being the bottom water will be taken up by the dip tube. The water might be hot now, but soon it will turn cold because the cooler water from the top will fill up the tank again. 

This way, you are not getting your desired hot water but also wasting the energy and efficiency of the water heater. So it would be beneficial to read the instructions given by the manufacturer before proceeding with the work. 

Crossover of the Water Line

Well, don’t get startled by this evaluation. All of a sudden cold water is coming out of your hot water. It happened due to the failure of the cartridge in anyone of the faucets of your house. 

You can find the cartridge in one-way faucets. They create some mix up which leads them to control the water system.

A Solution To The Crossover 

It is essential to get the Crossover of the waterline fixed as the main problem is the cartridge. 

Things Needed for the Work 

We won’t be needing many things to get the work done, just a cartridge, the puller, screwdriver, and some needle-nose pliers.

The Process

  • Turn off your house’s water system or the area you will be working in if possible. After that, let the water get drained from the pipes as they may create a problem when removing the cartridge.
  • While removing the knob, you may find sets of Philips screws that, when removed, pull the handle.
  • Things might come out while you are working in the faucet. You can use a paper towel not to lose them to plug the drain.
  • Pull the knob off when all the screws are removed.
  • Now comes the plastic hot water limiter; its work is to set the maximum hot mixture used in the faucet, and if you are ok with the position it is set in, then put them in the same way when you want to replace them.
  • Next is the removal of the washer and the cartridge sleeve.
  • To pull the pin on the cartridge, use the needle-nose pliers.
  • To unscrew the Philips screw use the puller specially used for cartridge removal from the back. After that, make sure the teeth are upfront and exposed as they will wrap around the plastic sides of the cartridge.
  • Now that it is set, screw the Philips screw in the faucet handle. Now take off the nut portion of the cartridge by the puller. That will pull out the cartridge a little you need to pull and shimmy it out.
  • As the cartridge removal is done, use the lubrication that came with the new cartridge to grease the rubbery seals and liner on the new cartridge.
  • Install the new cartridge. After that, you will see two things: Icy Hot and cold engine aligned together; push the cartridge back inside. 
  • Put the things that have been appropriately removed, like the cartridge sleeve and all the things cleared.
  • Now, as everything is set correctly, turn them a couple of times to see that they are correctly working or not done. 

Faulty Faucet

We know that cartridge is the main problem of crossover waterlines. But there is another way that a crossover waterline can occur, and that is any of the single-handed faucets is damaged.

There are two ways to find it. One is to open up all the single-handed faucets and turn on the cold side. If one of them is found hot, then that is faulty as it is said that usually, the one with the fault doesn’t provide cold water.

Another way is if you used the faucet that you didn’t use for a while, giving you a crossover problem, then that is the problem one.

Other Ways to Identify

Above, you guys got a brief idea of what problems you can face when you have no idea about the water lines. So to prevent all those, this is the other way of telling which water line is hot and cold on the water heater.

Running pipe 

Identifying the cold water line of the water heater is the easiest. The running pipe in the heater is the cold water line.

The Line From The Heater To The Rest Of The House

The line that starts from the heater and surrounds the rest of the house is the hot water line. Usually, both of the lines are placed at the top. But the hot water line is precisely placed at the top as soon as it gets heated, and it raises at the top automatically.

Left and Right

It should be the easiest way to scout out the water lines if they are correctly placed. The left side is the hot one, and the right side is the cold one. So make sure that your lines are set in the right place.


Above, we discussed how to tell which water line is hot and cold on water heater. The ways of identifying are pretty simple. Usually, both the waterlines are marked with specific letters, but if that is not done, you can look for the line both with and without something connected to them.

Hopefully, identifying the waterline and the problems that may occur are understandable. Read and remember them correctly while working with them.

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