Home Tool Guide Direct Hot Water Cylinder Buying Guide

Direct Hot Water Cylinder Buying Guide

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Direct Hot Water Cylinder

Electric storage water heaters that vary in size from 50 to 200 liters are known as direct hot water cylinders. Looking at the total number of people in your household, the element and anode rod type, and the type of water you have where you live when selecting a direct water heater. Could you continue reading for our best advice?

Important characteristics

There are four steps to selecting a storage water heater

To select the correct hot water cylinder, you don’t need to know everything there is to know about water heaters. The four(4) points listed below will help you in selecting the best direct water heater for your needs:

  1. Whether you install a vertical or horizontal cylinder depends on the size of your room.
  2. Seventy-five liters for one person; 100 liters for two people + 50 liters for each additional person.
  3. Choose from single and dual-element water heaters, as well as low- to high-density models.
  4. Entry-level sacrificial anode rods for medium-hard water; impressed current rods for hard water; anode rods; anode rods; anode rods; anode rods; anode rods; anode rods; anode rods; anode

Features that ensure safety

  • Thermostatic mixing valve: to keep the water temperature at the outlet below 50°C.
  • Temperature/pressure relief valve: controls the pressure in the cylinder.

Hot water cylinder components

Acrylic exterior wood paints

Electricity powers direct water heaters, also known as hot water cylinders. They are made up of the following components:

  • alined tank with a volume estimated in liters (l) based on the household’s hot water needs;
  • an inlet and an outlet for water;
  • The water is heated by a single or dual immersion element(s);
  • a thermostat for setting temperatures and activating the immersion heater to heat the water;
  • an anode rod for corrosion resistance;
  • supply of electricity
  • a control panel;
  • (Optional) LED light
  • a dip tube to ensure that your water is evenly heated and circulated

Choosing a size for a hot water cylinder

The capacity of hot water cylinder: 50 to 250 liters

Your cylinder’s capacity is solely determined by the amount of hot water you use and the number of people in your household. In general, 50 liters per person should be budgeted for. Nonetheless, it’s important to remember that a shower uses 30 to 60 liters of water, while a bath will use up to 150 liters.

  • Another 5 liters can be used to wash the face. Another 30 liters can be used by running the dishwasher. In general, if anyone in your house showers, washes their hands with cold water, and has a dishwasher, 50 liters per person should be enough. However, measuring 50 liters per person can result in a few cold showers if you baths, washes your hands in hot water frequently, and washes their dishes under running water. Choose a cylinder that is on the larger side in this situation.

calculating the power of your hot water cylinder

a simple guide

Number of people


One adult*

50 l

1 adult + 1 child

75 l

Two adults

100 l

2 adults + 1 child

150 l

2 adults + 3 children

200 l

2 adults + 3 children

250 l

2 adults + 4 children

300 l

*Adding 25 liters to account for any unforeseen spikes in hot water consumption is a brilliant idea (guests, etc.).

Consumption of hot water formula

Use the following formula to make your measurements more precise: first, you must determine your average daily water intake using a water meter. The water you use will usually be restricted to 40°C, while the hot water tank will be about 65°C. To calculate the amount of hot water drawn from the tank, multiply the total water intake by 1.8.

Why are you dividing this number? Simply because you can never use as much hot water as you think because you will always mix your hot water with cold water.

Hot water cylinder, vertical or horizontal

Choosing a location for your hot water cylinder installation

Since hot water cylinders take up a lot of space, it can be challenging to find room for them in your house. Manufacturers, fortunately, have a variety of shapes to suit all needs.

The shape of a cylinder

The most popular form of hot water cylinder is the vertical cylinder. If the design of your home does not allow for a  hot water cylinder, a horizontal cylinder can be purchased. These tanks may be mounted on the ground in a roof room, on the ceiling (if your ceiling height permits), or on a wall.

Please note that you must choose a model with a 50-liter capacity more significant than the equivalent vertical cylinder. These hot water cylinders have a total of just 200 liters.

It stands for a hot water cylinder

Fixture To A Load-Bearing Wall​

Storage water heaters are large and heavy since they hold a lot of water. Fixing plugs may be used to secure cylinders weighing up to 200 kg to load-bearing walls.

Installation of cylinders with a capacity of more than 100 liters

Any cylinder larger than 100 liters that cannot be mounted on a load-bearing wall should be supported by feet or a cradle.

Installation of cylinders with a capacity of more than 200 liters

Any cylinder with a total of more than 200 liters must be placed on a stand. Check to see if your floors will support the weight of your tank (this isn’t always the case in older properties).

cylinders for hot water that are extra-flat

Extra-flat or space-saving hot water cylinders are also available. These are made to fit into tight spaces. These tanks are more costly, despite their attractiveness.

Density elements with a low density vs. those with a high density

Low density and high-density elements are the two groups of elements.

Heating items with a high density

These elements have a small surface area and produce a great deal of heat. Owing to their limited surface area, high-density components collect more lime size. They are only recommended for use in soft to medium water areas because as the element degrades, your electric consumption will rise.

Heating elements with a low density

These elements have a larger surface area than their high-density counterparts and use the same amount of energy. These components do not wear out as quickly because they have a greater surface area. They generate less heat per square inch than high-density elements, so limescale builds up more slowly. If you live in a region of hard water, this is a vital consideration.

Thermostats are devices that regulate temperature.

A thermostat regulates the temperature based on preset temperatures, which are held by the heating elements.

Anode rods for water heaters

The tank of your water heater has a glass lining that protects it from corrosion. This lining, on the other hand, might have tiny cracks where rust can form. Both hot water cylinders have an anode rod that serves as an anti-corrosion system to prevent these micro-cracks from corroding (known as cathodic protection).

Water that is hard vs. water that is soft

Hard water absorbs a lot of limescale due to its high mineral content (200 mg of calcium carbonate per liter). Soft water has a lower calcium and magnesium content than hard water, which means it contains lesser limescale (60-120 mg of calcium carbonate per liter). The combination of hardness and acidity in water decides how corrosive: soft water (which is more acidic) is more corrosive.

Please note that you must choose a model with a 50-liter capacity more significant than the equivalent vertical cylinder. These hot water cylinders have a total of just 200 liters.

Rods anode

Anode rods made of magnesium or sacrificial anode rods

To secure the tank, the magnesium in the anode rod absorbs corrosive particles. The first generation of anode rods, sacrificial anode rods, was used in low-end storage water heaters. These anode rods are best used in places where the water is moderately rough. You’ll need to repair the anode rod until it’s worn out. Be warchfull on your anode rod to make sure it hasn’t worn out too soon.

Present anode rods impressed

These titanium anode rods are powered by electricity and produce a low voltage current that prevents corrosive particles in the water from attacking the tank’s metal. These anode rods are not sacrificial and can only be used in places where the water is tough.

Device hybrids

Going with the action of the two elements, these anode rods are made of titanium with a magnesium coating. An electrical current is used to send magnesium to weak points in the tank. Since they are more resistant to corrosive and hard water, hybrid systems are called high-end anode rods.

What is the purpose of an anode rod?

It’s worth remembering that having some hardness in your water will help protect your hot water cylinder. Though hard water reduces the efficiency of your water heater, soft water corrodes your cylinder more efficiently and reduces its service life. A sacrificial anode rod can quickly degrade, and even impressed current or hybrid systems can have a shorter service life than advertised.

If you have a water softener, configure it to the manufacturer’s recommended settings. Water with 60 mg/l calcium carbonate is considered soft; water with 60–120 mg/l is moderately complex; 120–180 mg/l is hard, and moisture with more than 180 mg/l is tough.

Accessories for installing a storage water heater

Storage water heaters come with a variety of installation accessories and safety features, including:

  • Dielectric unions are used to prevent corrosion between two different metals.
  • Excess water from thermal expansion is stored in an expansion tank. Since the water is not lost but instead reintroduced into the circuit, you will be able to save money. For a cylinder capacity of 100 to 150 liters, an 8-liter expansion tank is required. An 11-liter expansion tank is needed for a cylinder capacity of 150 to 200 liters, and a 25-liter expansion tank is needed for a cylinder capacity of 200 to 300 liters.
  • A temperature/pressure relief valve (or T&P valve) must be mounted to relieve excess pressure or temperature.
  • The cylinder’s water is released through a drain valve.
  • When draining or inspecting the cylinder, a shut-off valve is required to manage incoming water.
  • The water temperature at the water heater’s outlet is limited to 50°C by a thermostatic valve.

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