Why does the water get lukewarm with a water-saving showerhead? A thorough guide to choosing the right one and troubleshooting!
“I switched to a water-saving showerhead to save on water and gas bills, but the water feels lukewarm...” “I’m having trouble because the water suddenly turns cold while I’m in the shower...”
Have you ever experienced this? You were excited to save on your monthly utility bills, but it’s a shame if your bath time becomes cold and uncomfortable.
“Is the new showerhead defective?” “Or has the water heater broken down?”
You might feel anxious, but in most cases, it is neither a faulty showerhead nor a broken water heater. The main cause is “insufficient operating flow rate,” where the water-saving showerhead restricts the water volume so much that it falls below the amount required for the water heater to operate normally.
In this article, we will explain in a clear and detailed manner the mechanism behind why water becomes lukewarm with water-saving showerheads, the points you must check before purchasing, how to choose without making mistakes, and the steps to take if the water does happen to turn lukewarm.
Let’s choose the perfect showerhead for your home environment to enjoy both a comfortable bath time and smart savings.
Furthermore, detailed compatibility information between water heaters and showerheads, as well as a troubleshooting checklist for various issues, are introduced in the following explanation page. Please be sure to refer to it as well.
The main mechanism behind why water becomes lukewarm with water-saving showerheads
First, let’s unravel the reasons why water becomes lukewarm or cold when you switch to a water-saving showerhead. Knowing the mechanism will help you stay calm and deal with the situation if a problem occurs at home.
Because the water-saving structure reduces the amount of water
Water-saving showerheads are designed to restrict water flow by making the holes where water comes out (spray holes) smaller or by reducing the number of holes. Some products also have a valve inside the handle to automatically control the water volume. By doing this, even if you turn on the shower as usual, the “total volume” of hot water actually passing through the hose is significantly reduced.
Because it falls below the “operating flow rate” of the water heater
The gas or oil instantaneous water heaters used in homes are designed to trigger the “heat water switch” when water passes through the pipes. There is a sensor inside the water heater that detects the movement of water, and it will not ignite unless a certain amount of water flows. This minimum amount of water required for ignition is called the “minimum operating flow rate.” If a water-saving showerhead restricts the water volume too much, it falls below this minimum operating flow rate, and the water heater’s sensor determines that “no water is flowing.” As a result, the water heater may not ignite or the flame may go out midway, causing cold water to come out.
Be especially careful in summer or when you first start using hot water!
In summer, when the water temperature is high, the water heater requires less energy to heat the water to the set temperature, so the device automatically adjusts the water volume in detail. When the control of a water-saving showerhead is added to this, it becomes even easier to fall below the operating flow rate. If you find that the water suddenly becomes lukewarm only in summer, this may be a major factor.
“Water pressure” and “flow rate” are completely different things!
Here, let’s talk about a major misunderstanding that many people fall into. That is the confusion between “water pressure” and “flow rate.”
“The shower force is strong enough, so why does the water heater flame go out?”
Many people might wonder about this. In fact, “force of water (water pressure)” and “amount of water actually flowing (flow rate)” are completely different, even though they seem similar.
If you squeeze the end of a hose with your fingers, the water will fly far with great force. However, the total amount of water coming out from the base of the hose has not increased. Rather, because you narrowed the exit, the amount of water flowing per second has decreased.
Water-saving showerheads work on the exact same principle. By making the spray holes smaller, the "force (water pressure) hitting your skin" feels stronger, but the "amount of water (flow rate)" passing through the water heater is significantly reduced. Even if it looks like the water is coming out vigorously, the water heater may decide to turn off the flame because it detects that very little water is flowing. This is the true cause of the phenomenon where the water feels lukewarm despite having strong pressure.
Why mist showers feel cold and how to tell the difference
The "mist-function showerhead" has become very popular recently. While it is reputed to be gentle on the skin and effective at removing dirt from pores, we often hear people say that the mist feels cold. There are two possible reasons for this.
Reason 1: The mist loses heat in the air (heat dissipation)
When water turns into a mist, the droplets become extremely fine. As the droplets get smaller, their surface area exposed to the air increases many times over, causing heat to escape into the outside air in the brief moment between leaving the showerhead and reaching your skin. This is not due to a malfunction of the water heater or insufficient flow, but is caused by physical cooling. If you bring the showerhead closer to your body (about 15 cm), it will start to feel warm.
Reason 2: The misting reduces the water volume, causing the water heater to turn off
Another reason is, again, insufficient flow rate. Because mist discharge restricts the water flow to an extremely fine level, the flow rate is even lower than that of a normal straight stream. This can cause the water heater to shut off.
A simple check to identify the cause!
If you feel the water is lukewarm while using the mist setting, try turning the dial to switch to the "normal straight stream" setting.
If the water becomes warm immediately after switching back to the straight stream, your water heater is working properly. The cause is "heat dissipation of the mist in the air," so you can solve this by slightly increasing the water heater's temperature setting (by about 2–3°C) or by using the shower closer to your body. If the water does not get warm even after switching back to the straight stream, or if the burner icon on the remote control has turned off, the cause is "the water heater stopping combustion due to insufficient flow rate."
Check this before you buy! Points to verify for your faucet and water heater
To ensure you choose the right showerhead without failure, it is essential to check your home's equipment environment before clicking the purchase button. Make a note of the following points.
1. Check the manufacturer and model number of your faucet and water heater
Check the front of your faucet, under the lever, or on the crank part near the wall for any engravings or model number stickers. Also, there is a sticker with the model number on the front of the water heater unit located outdoors or on your balcony. If you know the model number, you can easily check specifications such as the "minimum operating flow rate" in the manufacturer's instruction manual or on their website.
2. Check the screw standard for the hose connection
The screw standard at the connection between the showerhead and the hose is also important. Many brands like TOTO and LIXIL (INAX) use a standard specification (G1/2), so you can replace them by hand. However, for manufacturers like KVK or MYM, the screw threads are different, so you will need to use the included "conversion adapter." Be sure to check if an adapter is included with the product you intend to purchase.
3. Check if it has a hand-held stop button
Showerheads with a button that allows you to stop the water instantly at your hand are very convenient, but they cannot be installed on just any faucet. Installing one on an old two-handle mixing faucet that lacks a "check valve (a safety device that prevents the backflow of water or hot water)" is very dangerous, as it could cause pipes to burst or cold water to backflow. Please be sure to check if your home's faucet has a check valve.
4. Precautions when using an EcoCute system
Due to their structure, storage-type EcoCute systems release hot water through a pressure-reducing valve, so they tend to have lower initial water pressure compared to direct-pressure gas water heaters. If you combine this with an extremely high water-saving head that exceeds a 50% water-saving rate, the shower pressure may become very weak or the water may easily become lukewarm. For households with EcoCute, we recommend choosing models labeled as "low water pressure compatible" or products with a more moderate water-saving rate.
Don't make a mistake! Smart comparison criteria for water-saving showerheads
With so many water-saving showerheads available in stores and online, it's hard to know which one to choose. We've organized the key comparison points to help you avoid mistakes.
Don't choose based on water-saving rate alone! "Balance" is most important
While numbers like "50% water savings!" or "60% cut!" sound attractive, products with excessively high water-saving rates restrict the water flow so much that they can easily cause ignition failure in water heaters. If you are concerned about your home's water pressure or want to prevent water heater ignition issues, choosing a balanced model with a water-saving rate of around 30% to 40% is the safest choice and the one you are least likely to regret.
Choosing one with a "water flow switching function" is safer
Models that allow you to switch between multiple water flows, such as straight, mist, and jet, are more convenient than types with only one flow. Even if the water temperature drops when using the mist setting, you can easily maintain the water heater's combustion by switching back to the straight setting.
If you live in a rental property, never throw away your "original showerhead"!
If you live in a rental apartment or condo, please do not dispose of the original showerhead or gaskets you removed; keep them in a safe place. You have an obligation to "restore to original condition" when moving out. If you cannot put it back, you risk being charged for the cost, and it can also be used for a comparison test to determine if a problem is with the water heater or the showerhead if the hot water stops working in the bathroom.
Steps to check when you feel the water is lukewarm after replacement
If you feel that the water is lukewarm after switching to a water-saving showerhead, try checking in the following order.
Switch back to the original showerhead and compare First, try switching back to the showerhead you were using before. If the water gets nice and hot with the original head, the cause lies in the flow restriction of the new head. If it is still lukewarm with the original head, you can conclude that it is highly likely to be a failure or setting issue with the water heater itself.
Switch to normal flow and measure the water volume with a bucket If you can switch the water flow, try returning it to the normal flow setting. It is also recommended to catch the water in a 10L bucket for one minute to measure the actual amount of water coming out. If it is less than 5L to 6L per minute, it is a sign that the water heater can no longer maintain ignition.
Clean the strainer and check the stop valve If limescale or debris is clogged in the showerhead mesh or the filter (strainer) at the faucet connection, the flow rate will drop. Try cleaning it with a toothbrush or similar tool. Also, if the stop valve at the base of the faucet is tightened too much, try opening it slightly with a flat-head screwdriver to increase the water volume.
Check the water heater for error codes Check if there is an error code displayed on the water heater's remote control screen. If an error indicating ignition failure or flameout appears, check the instruction manual, and try re-igniting by raising the set temperature by 2-3°C or increasing the water discharge volume.
Consult a professional if it does not improve If the situation does not improve after performing these checks, do not try to disassemble it yourself; consult a professional. It is smoothest to contact the appropriate party, whether it be the showerhead manufacturer, the water heater manufacturer, or a plumbing contractor, depending on the situation.
Summary: Start a comfortable water-saving life with the right knowledge!
The main reason why water becomes lukewarm with a water-saving showerhead is not a lack of water pressure, but rather "the inability to meet the minimum operating flow rate of the water heater."
To avoid mistakes, it is most important to choose a product that is appropriate for your home's water heating system (gas instantaneous, EcoCute, etc.), water pressure environment, and faucet specifications, rather than just choosing based on the water-saving rate.
Before purchasing, check the model number of the faucet and water heater you are currently using and make sure to confirm the compatibility conditions.
For more detailed mechanisms, comparison points for each facility environment, and specific inspection procedures, we introduce them on the following site with photos and easy-to-understand explanations. Please take a look to help you choose a showerhead without any regrets!
With the right knowledge and preparation, you can enjoy a comfortable, water-saving lifestyle without any regrets!
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