Why Isn’t the Hot and Cold Water Mixing in My Shower?


1. My Tankless Water Heater Flips From Hot to Cold

As you are taking a shower, you may notice that there are breaks in the flow of hot water when someone flushes a toilet or washes their hands. This can be dangerous if you increase the temperature setting, which can result in scorching hot water coming out of the showerhead.

How to Fix Your Tankless Water Heater That Flips From Hot to Cold

You can call out to your family to hold off on running all other faucets in your home while you shower. You can also make sure that washing machines and dishwashers are off.

The hot water pressure is often lower than the cold, so you can solve this with a flow restrictor. A flow restrictor balances out the water pressure and can help prevent rapid temperature changes.

It is dangerous to have the heating element running on a tankless heater without a constant flow of water. For low pressure, you may need to install a pump to bring the pressure back up. Or you can install a tankless heater that will pressurize the water as it heats.

2. There Is No Hot Water Coming Out

Rust and limescale will block up the hot water pipes before the cold pipes. Scale, deposits, and wear and tear are common issues with faucets. Hard water will leave calcium deposits around the spout of the faucet.

How to Fix a Hot Water Blockage

A tankless water heater activates when someone turns on the hot water tap. This pressure release turns on the electric or gas heating element and heats up the water. Low water pressure can fool the heater into thinking that the water is being turned off and will stop the heater.

Immersion heaters use convection to mix the water, cold water goes in the bottom, and hot water drains near the top. Some immersion heaters route the cold water in through the top and down a long dip tube to the base of the tank.

If the dip tube is broken toward the top of the tank due to corrosion, the cold water will not mix and drain cold water straight out to your hot water pipe. This dip tube is replaceable but difficult to reach, and problems often mean replacing the whole unit.

3. My Hot Water Flow Rate is Poor

If you turn on your shower, and there is a dribble of hot water coming out, but the cold is fine, it is a blockage. Blockages can occur anywhere along the pipe and even at the tank, but you should start with the faucet.

How to Fix Poor Hot Water Flow Rates

The shower cartridge will wear out over time even if the water is soft and prevent you from getting hot water. You can descale the faucet by taking out the cartridge and soaking it in warm vinegar or a descaling solution for a few hours.

Be prepared, as the descaling process may open up leaks and cause other problems. If the flow of hot water is so bad that the hot water drips out, you are better off buying a new faucet. Single cartridge showers look nice, but they are troublesome; double cartridge showers are much easier to maintain.

4. The Water Is Colder Than Normal

An immersion heater has a large electric heating element running through the middle of the hot water tank. The metal encasing these elements is prone to splitting from the build-up of limescale around them, as you would get in a kettle.

A small hot water tank, with enough for one person to have a quick shower, will quickly run out of hot water. Small tanks may try to keep up, but the inflow of cold water will keep bringing the temperature down.

Even with a large hot water tank, someone having a bath will use a tank full of hot water, and large tanks take a long time to heat fresh cold water.

How to Fix Colder Than Normal Water

You can first try reducing or removing limescale from the system. But first, check to see the thermostat setting, as it could be that someone has lowered the temperature. immersion heaters also have thermostats – these are sometimes on the tank itself.

If you are trying to avoid the cost of running the heater all day for hot water, you can try a timer. You can set an immersion heater timer for an hour in the morning so that you can have a hot shower before the day begins.

The simple solution for a small water tank is to get a bigger hot water tank – if you have the space. The alternative is to move to a tankless water heaterOpens in a new tab. that heats the water on demand. Tankless water heaters are efficient and perfect for small homes.

5. The Flow of Hot Water Is Inconsistent

If you are struggling to get the shower to reach a comfortable temperature, there may be a few reasons behind it. Flow restrictors can cause issues when they malfunction. The flow restrictor can cause pulsing water or inconsistent ratios of hot and cold.

The heating pipes of tankless flow-through water heaters can also clog up with sediment and limescale. Over time this can slow and even halt the flow of water through the heater.

How to Fix an Inconsistent Flow of Hot Water

If you have a flow restrictor, you can try and open it up further to increase the pressure in the system. You can try descaling your pipes, but you may still need to replace the flow restrictor.

As an active measure at reducing limescale, you can attach an electronic descaling systemOpens in a new tab. to your main water supply. A descaler will protect your whole home’s water supply preventing blockages and ruptures. Descaling units also protect home appliances such as washing machines and dishwashers.

If you already have a scale guard but still suffering from scale, you should check to see that it is still working. If your scale guard is still working, try moving it along the pipe to see if there is a build-up in deposits further back to the source.

You can try a descaling kitOpens in a new tab. for tankless heaters – this will flush out the limescale, rust, and muck from the system. The kit will take around 45 minutes, and it should keep the system clear for up to 2 years.

Graham Walsh

I want to share everything I know about home improvement in order to help you. Whether you're a home enthusiast or an industry professional, I have the information that you need.

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