What Additional Parts Do I Need for My New Hot Water System?

  • By Hot Water Boss

Published: Friday, September 12, 2025

What Additional Parts Do I Need for My New Hot Water System?

When replacing or installing a new hot water system, it’s not just the tank or heat pump you need to consider. To ensure your system runs safely, efficiently, and remains under warranty, it’s essential to replace all valves and fittings at the same time.

 

Using old valves on a brand new system may look fine, but it generally leads to performance issues, safety risks, and even voids your warranty. At Hot Water Boss, we make sure every installation includes the right components for a fully compliant system.

 

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Key Valves and Fittings for Hot Water Systems

Tempering Valve

A tempering valve is a mandatory safety device that blends hot and cold water to deliver a safe outlet temperature (approximately 50°C).

- Required under Australian Standards (AS 3500).

- Prevents scalding.

- Legally required in Queensland when replacing a hot water system.

Pressure Limiting Valve

A 500 kPa pressure limiting valve must be installed on the cold-water line. This protects your hot water system from:

- Excessive water pressure.

- Internal damage to your unit.

- Voiding of your warranty.

Duo Isolation Valve

A duo isolation valve is both an isolation valve and a non-return valve. It:

- Isolates the cold water supply to your hot water system.

- Prevents water from flowing backwards into the main supply.

Cold Water Expansion Control Valve

This valve is fitted to the cold-water side of the system to:

- Release excess pressure buildup.

- Protect system components from damage.

- Maintain compliance with plumbing regulations.

Concrete Base (Ripple Pad) or Pizza Base

Your hot water system must be installed on a solid base to:

- Allow airflow around the bottom of the tank.

- Provide stability and protection from ground moisture.

- Ensure compliance with Australian Standards.

Pipework Lagging

Thermal insulation (lagging) is applied to hot water pipework to:

- Reduce heat loss.

- Improve energy efficiency.

- Meet Australian energy regulations.

Safe Tray and Water Shut-Off Valve

Depending on where your hot water system is installed, these may also be required:

- Safe tray: Prevents water damage in case of leaks.

- Water shut-off valve: Allows quick isolation in emergencies.

Other Essential Fittings

In addition to valves, other fittings and consumables may be required for installation, including:

- Copper pipe.

- Thread tape and sealants.

- Assorted connectors.

Why Valves and Fittings Matter

Every hot water installation must comply with AS 3500 and the manufacturer’s specifications. Using the correct valves and fittings ensures:

- Warranty protection.

- Safe and efficient operation.

- Compliance with Australian plumbing standards.

 

All work must be carried out by a licensed plumber.

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👉 If you’re shopping for replacement components, browse our valves and fittings collections.

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Frequently Asked Questions

What size hot water system do I need?

While the size of the hot water system will more than likely vary depending on your specific needs, the average 4-person Australian home will need at least a 160 litre tank for a continuous electric system, or a 250-315 litre off-peak system. If you’re in the market for a gas tank, a 4-person house averages a 170 litre tank. 270-315 litre tank should be sufficient for heat-pump users. 

Why is the right size hot water system so important?

If your hot water heater is too small for your needs, you will find yourself continually run out of water. On the other hand, if your hot water system is too large for your needs, you are going to spend an unnecessary amount of energy (and therefore money) heating it. This is because your hot water system will keep maintaining the heat of your water, even when you are not using it.

Can I install the system myself?

You will need a licensed plumber to install your new hot water system.

I'm not in SEQLD - how do I choose a plumber?

It's important to ensure you choose the right plumber to install your hot water system. The last thing you want is a non compliant install on your brand new hot water system, which could shorten the life of the new hot water system and even void the warranty. We are often asked if a customer can install a hot water system...in all honesty the risks aren't worth it - and it's illegal! Best to call a licensed plumber to ensure it's done right.

How do I calculate my hot water usage?

The first step to take in choosing a new hot water system is to calculate the hot water usage in your home. The amount of hot water each household uses will vary depending on lifestyle, appliances, and water fixtures throughout the house. 

Complete Hot Water System Installation Kit

Non-return & Isolation valve

Pressure limiting valve

Expansion control valve

Tempering valve

All necessary accessories and fittings

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