Why Does My Shower Go From Hot To Cold: Let’s Find Out

Beginner Info, Tankless Water Heater

why my shower goes cold from hot
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It goes without saying that tankless water heaters are in demand in not only the USA but various parts of the world.

However, a lot of my clients have to face the issue of the showers going from hot to cold.

And, in case, you’ve landed on this page, then I’m assuming that you’re also facing the problem of the shower getting cold from being hot, right?

Needless to say, it horrified your experience and makes the situation bizarre, isn’t it?

I’ve also been a victim of the shower getting cold, and the worst part, that time I was residing in extremely cold climatic conditions.

Just think of, how badly I was hit, and trust me, it was not once or twice rather it becomes a frequent affair, and I had no option but to find a tangible solution to get rid of this idiosyncratic problem.

Like me, many of the avid readers of this blog would’ve faced the hot water temperature fluctuation problem while taking a relaxing shower, isn’t it?

Let’s find out how to deal with the fluctuating temperature in an effective way.

Tips To Deal With Fluctuating Water Temperatures Effectively

What all the tips that I’m gonna share with you in a while had helped me and my clientele in getting rid of the water fluctuation problem.

And, we’re quite confident that you’ll also get benefitted from the same.

Check Your Water Heater Type And Size

Trust me, one of the main reasons for the water fluctuation is the sizing of tankless water heater done wrongly.

Either you’ve opted for a less flow rate or a higher one, in both the case, you’ve done the mistake.

For example, the common symptom of an underpowered tankless water heater is fluctuation and unexpected hot water supply.

Whether you’re planning to opt for an electric tankless heater or its gaseous version, in both cases, you need to do proper homework and come up with the correct sizing so that the hot water requirement of your home would be sufficed in the best possible manner.

We asked a couple of questions related to the water fluctuation problem and asked our clientele to share their water requirements and the tankless heater that they were currently using.

Trust me, the response which I got said all about the problem itself.

Most of the clients who were having water fluctuation problems were either using a low-powered tankless heater or were residing in extreme climatic conditions.

Here, you need to also understand that your flow rate required for a warmer climatic condition is different from that of an extremely cold climatic condition.

For example, a flow rate of 7 to 11 GPM would be sufficient to cater to the hot water requirements of a small-sized home to a medium-sized home in a warmer climate.

Unfortunately, the same flow rate wouldn’t perform as per the expectation in the cold climatic condition.

Can you guess the reason?

Well, the difference between the incoming groundwater/supply water and the outgoing hot water in climatic conditions is more as compared to a warmer climate.

So, more heat is required to raise the water temperature to the set output temperature, and as a result, the flow rate is impacted adversely.

So, if you’re a resident of an extreme climatic condition, then look for a more powerful tankless water heater like the one that Rinnai provides.

Uncontrollable Water Heating Is Serious

Many of the newbies and first-time buyers end up doing mistakes that involve uncontrollable water heating.

Trust me, it’s a serious issue and you need to deal with it in an intelligent and well-planned way to prevent any last-hour misadventure.

Have you isolated the problem?

The best way to isolate the problem is to do some random experiments.

What I actually do is, first test the water temperature with one fixture, it can be a shower or a faucet.

Choose the one that you’re comfortable with.

While you’re doing the water temperature testing, make sure that all the other appliances are switched off.

Well, if your water temperature is condition is consistent with the aforementioned condition, then the problem most probably lies with other variables.


You need to test two showers for the hot water by keeping all other water-consuming appliances in an off state.

If the outcome resembles temperature fluctuation, then we can conclude that the tankless water tank that you’re currently using is underpowered as per your requirement.

Did you inspected your water heater properly?

I suggest to all the readers of IzzySmartHomeGuide.com refrain from disassembling your water heater in the absence of expert plumbing experience.

What the best that you can do is, examining your water heater with a visual inspection in order to NOT ONLY identify problems but also check your water heater manual for safe maintenance instructions.

Does your tankless water heater possesses an emergency thermostat?

Well, if you’re not having an emergency thermostat in your tankless water heater, then definitely, you’re lacking some important feature.

As the name suggests, an emergency thermostat is important as it will play a crucial role in shutting off your tank during an unprecedented situation or an emergency condition.

Unfortunately, the problem could be even bigger if your thermostat trips very often.

Many of the newbies wouldn’t be aware of the fact that a broken thermostat usually isn’t the cause of fluctuating water temperatures.

And, even bigger problems are the faulty temperature regulators.

If your water temperature reaches a certain threshold temperature level, then your water heater will stop heating.

So, what all you need to do if your water heater is gas powered…

  • First and foremost, you need to check whether the pilot light is on or NOT
  • In case, you found the pilot light off, then try to relight it
  • Moving further, you need to turn the gas valve off, and wait for few seconds before you proceed to the next step
  • Now, you need to turn the gas valve to pilot position
  • I would suggest you should use either an ignition switch or a stick lighter in order to ignite the pilot light
  • As soon as the pilot light is on, the next thing that you need to do is to set the valve back to a standard position

Can moisture in the basement cause problem?

Definitely, the more the moisture density in the basement the bigger could be the intensity of the problem.

Frankly speaking, a flooded basement could be one of many reasons that can lead to malfunctioning or switching off of your pilot light.

You need to check carefully the electric breakers, in case, you own an electric water heater such as ECO 27.

The next thing that you need to do is to restart your electric tankless heater but before that, you need to flip your breaker back.

However, my advice to you would be to consult a professional in case, your heater is continuously tripping the circuit breaker.

What is the ideal temperature for hot water?

“In a recent article from the Wall Street Journal, it was determined that 112 degrees Fahrenheit was the ideal temperature for hot water. Hot water heaters can provide water as high as 140 degrees”.

Moreover, we consulted quite a few doctors to find out what actually is an ideal temperature.

From the responses that we got, all that we can conclude is there is no hard and fast rule for an ideal temperature.

However, most doctors recommend setting the hot water temperature at 120 degrees or below that in order to avoid problems related to dry skin.

In fact, the risk of damaging the skin’s lipid layer increases multiple folds as soon as hot water temperature surges above 112 degrees benchmark.

Unfortunately, the replacement of the lipid layer becomes very difficult as you grow older and older.

The aforementioned statement is quite evident from the fact that older people tend to suffer more from dry skin.

Is Your Tankless Water Heater Causing Water Fluctuations?

To be honest, market is flooded with a wide range of tankless water heaters.

From whole house tankless water heaters to commercial counterparts, you’re gonna find a tankless water heater for every requirement that you’ve got in terms of hot water.

As we all know, tankless water heaters don’t store hot water rather heat it whenever the end-users require it.

The mechanism, lifespan, performance, and efficiency are perfect ONLY IF you’ve successfully done the sizing correctly.

Already, we had enough discussion on why sizing is so important.

The main cause of a tankless water heater fluctuation in the water supply is it being underpowered.

So, you need to contact a certified professional and discuss whether you need to upgrade your tankless water heater with a high gallon per minute or NOT.

Checking Pressure Balancing Valve Is Important

Irrespective of you being a newbie or a seasoned professional, it is really important that you pay attention if you notice water temperature fluctuation.

So, how to figure out that the pressure balancing valve is the main culprit?

Well, it’s easier than you think.

All you need to do is to ask your friends, family members, or someone else to start your washing machine, dishwasher, or flush your toilet while you’re taking your shower.

And, if you found fluctuation in the temperature of your shower, then perhaps the pressure-balancing valve isn’t working fine.

Depending upon the water flow in the plumbing system, a pressure-balancing valve opens and closes.

And, if you found a drop in the level of either cold or hot water, then the probability is very high that a broken pressure valve is behind this issue.

However, it is a simple problem, and trust me, replacing the pressure-balance valve wouldn’t cost you a fortune.

Before you’ve made up your mind for the replacement my sincere suggestion would be to hire a professional to get the appropriate and helpful suggestion.

Wrapping Up

First and foremost, I would like to thank you for being with us till the end.

Secondly, I would like to bring to your notice that I along with my core team have put loads and loads of effort into coming up with this idiosyncratic superlative piece of information.

And, in case, you’ve gained something from our efforts and want to appreciate us, then feel free to share this piece of information with the ones who are in need of it.

After all, sharing is caring, isn’t it?

To conclude, I don’t deny the fact that there could be numerous reasons for showering going cold from hot.

However, what we found out is, underpowered tankless water heaters are the most common reason for a shower going cold from hot.

Please do let us know if you found reasons other than the one mentioned in the post behind the shower becoming cold from hot.

That’s all, as of now :):)

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