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If you are struggling with hot water in your home or business, a new hot water heater may be your answer!

Purchasing the right sized hot water system is essential as otherwise, you might end up with a minor system that does not meet your needs. There are different sizes of hot water systems available, and you will even get tankless variants.

We have spoken about each of the types in detail to help you make the right choice. We will discuss tankless hot water heaters and then heaters with tanks.

Tankless variants work well for tiny houses and apartments, while tanks are required for organisations, factories, or large homes. We’ll explain how to measure the hot water needed in the following sections, so let’s begin.

What Size Hot Water Heater Do You Need?

A. Tankless Water Heaters

If you live in an apartment or a small house, large water tanks may not fit in. A 190-litre water tank can be six feet long and 22 inches wide, which is huge. For such cases, you can always opt for a wall-hung water heater without a tank.

These can be connected to the pipelines to get hot water from your taps and showers. Also, they come in varying sizes, and you will find suitable options for small bathrooms.

To determine the size required, read through the following steps

Step 1: Calculating The Peak Hot Water Usage

To begin with, you will have to calculate the peak water usage in the house. It is usually calculated by considering the flow rate of all faucets or appliances in litres-per-minute or lpm. That will help you understand the flow rate needed from the tankless water heater.

  • Washing machine- 11.35 lpm
  • Dishwasher- 11.35 lpm
  • Bathtub- 11.35 lpm
  • Sink tap- 3.78 lpm
  • Shower- 9.5 lpm

You can calculate the peak water usage based on the busiest time of the day. If you use the bathtub and the dishwasher simultaneously, you will need a water heater with a 22.71 lpm flow rate.

Step 2: Finding Out The Temperature Of Water

The next determining factor includes finding out the average water temperature entering your house. You can use a thermometer to immerse it in the water collected from the cold water tap to get an accurate temperature reading.

Step 3: Understanding The Temperature Rise Needed

To do this, you will have to subtract regular water temperature from 43 degrees celsius. For example, if the water temperature in your house is 16 degrees, then the water heater will have to heat the water by 27 degrees before you use it. That is how you will get the required temperature.

When you purchase a water heater, it will have a hot water flow rate mentioned. If the water heater has a flow rate of 37.85 lpm, and the temperature rise required is 20 degrees, it might work at 37.85 lpm.

But if the temperature rise required is 40 degrees, then the flow rate is reduced to 26.5 lpm. Keep this in mind while purchasing, and you should not face any problems.

B. Water Heaters With Tanks

One can measure the size of the tank depending on the number of people who will use it. For example, if you have one to two people in the house, a tank size of 87 to 136 litres should work well. You will need a tank with 136 to 174 litres capacity for two to four people.

In a large family with three to five people, a tank size of 174 to 211 litres will work well. And if the family has five people or more, you can purchase a large tank of 211 litres or more. The trick is to add 37 litres for every individual added after that.

This measurement is for tank-style heaters, and most mid-sized families opt for a 150 litres tank, which is generally affordable and suits most purposes. However, you can always purchase a different size based on your family’s requirements.

Calculating The First Hour Rating

Along with the tank capacity, you will have to consider the first-hour rating of a hot water heater. The first-hour rating or FHR is defined as the amount of heated water produced by the tank within 60 minutes. The FHR should clarify how efficient the tank is and how quickly it heats.

While checking the FHR, you will have to see if it matches the number of litres of heated water the family needs. To calculate the amount of hot water needed around the house, we created a list that should include all the activities.

  • Shampooing per family member: 22.71 litres
  • Regular showering per person: 75.7 litres
  • Shaving: 11.35 litres
  • Washing hands per individual: 7.57 litres
  • Washing dishes manually: 22.7 litres
  • Washing machine: 113.5 litres
  • Dishwasher: 53 litres

Use this to calculate the amount of water needed and then purchase a water heater accordingly. Take the busiest part of the day and estimate the amount of water required because you may be using multiple appliances simultaneously.

Tips To Remember

This section will talk about some crucial factors to keep in mind while making a purchase.

1. Pay Importance To Showers

Showers use the most hot water, and it is important to measure the water usage. If you have a baby in the house, calculate half the water needed for an average human. Also, if you have someone in the house who takes long showers, calculate the water used accordingly.

2. Costs

Always take the costs into account to never pay a large amount of money for a hot water system. We have mentioned the average water usage in Australian households so that you end up purchasing the right-sized heater.

It is best not to go for a bigger size than required as you will be unnecessarily spending more money. The water will take more time to heat up, and operating costs will shoot up unnecessarily.

Also, if the heater has a water tank, it would take up a lot of space, which you can avoid if you control water usage.

3. Consult Your Local Authorities

If you are not sure about the water temperature throughout the year, you can always consult local authorities. They will help you by providing the details of the water temperature throughout the year or specifically at the coldest time of the year.

Choosing The Right Size Water Heater

If the place you live in experiences cold temperatures, then opt for a higher lpm than needed. The flow rate will automatically reduce when the temperature falls, but you should get ample hot water even on winter’s coldest days.

Keep this in mind before making a choice, and with that, we have reached the end of this guide, so it is time to wrap up. We hope you can purchase the right water heater for the house. Also, ensure that you get the hot water systems serviced once or twice a year to keep them from malfunctioning.

Whether you need assistance choosing the right water heater for your home, an installation or replacement, our Melbourne plumbers are here to help. At WP Plumbing, our team has years of experience with various brands and types of water heaters. Contact us today for all your plumbing needs!

Take care and stay warm!

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