Can I Run Two Showers Off A Combi Boiler?

Yes, running two showers at once with a combination Boiler is possible. The Boiler’s flow rate and capacity must be sufficient to supply hot water to both showers without compromising pressure or temperature. High-capacity Combi Boilers, such as those with 38-42 kW outputs, are better suited to meet this demand. Your main water pressure is a factor, and thermodynamic mixer showers will help balance temperature fluctuations. You can run two showers simultaneously with the right Combi Boiler and plumbing setup.

How Does A Combi Boiler Work?

Combination Boilers are the most popular Boilers installed in UK households due to their compact size and efficiency. Unlike system Boilers that rely on a separate hot water cylinder and traditional Boilers that rely on a cylinder and storage tank, a combi Boiler heats water directly from the mains.

This means you get hot water on demand for your shower, taps, or central heating. However, this design also means that the Boiler’s ability to supply hot water is directly tied to its capacity and the flow rate of your mains water.

For a single shower, a typical Combi boiler is more than capable. The challenge arises when you try to run two showers at once. In this scenario, the Boiler must heat and distribute water to two outlets simultaneously.

Key Factors for Running Two Showers

Running two showers from a combi Boiler is feasible as long as the following requirements are met:

Boiler Capacity

The Boiler’s output, measured in kilowatts (kW), determines how much hot water it can produce. For example, a Worcester Bosch Greenstar 8000 Life 35kW Combi Boiler can deliver a domestic hot water flow rate of up to 14 litres per minute. This is sufficient for two showers with low to moderate flow rates, but pressure and temperature may drop if both are used at full flow.

A larger-capacity Boiler (e.g., 38-42 kW) is better for homes where two showers are frequently used simultaneously. A larger Boiler will provide a higher flow rate, ensuring both showers receive an adequate hot water supply.

Water Pressure

The mains water pressure is an important factor. If the incoming cold water flow rate is below 15 litres per minute, even a high-capacity Boiler will struggle to deliver consistent hot water to two showers.

You can use a flow rate gauge or consult a plumber to check your water pressure.

Shower Types

The type of shower you have also affects how well your system performs. Thermostatic mixer showers are ideal for combi Boilers, maintaining a steady temperature even when water flow fluctuates.

Electric showers run independently of the Boiler, heating water directly from the mains. Electric showers are a good option if your Boiler can’t handle two simultaneous showers and you don’t want to install a new, more powerful boiler.

Usage Habits

Finally, consider how often two showers are likely to run simultaneously. If it’s an occasional occurrence, a standard combi Boiler should suffice. If two showers are used at the same time most days, a higher-capacity Boiler will be necessary.

Boilers That Can Serve Two Showers

Here are some Boilers that will meet the demand for homes looking to run two showers simultaneously.

Worcester Bosch Greenstar 8000 Life 40kW

This high-capacity combi Boiler is well-suited for medium to large homes.

Key Features:

• Flow Rate: Up to 16.4 litres per minute, providing a steady hot water supply.
• Efficiency: Rated ErP A, combining performance with energy savings.
• Smart Controls: Compatible with Bosch EasyControl for precise management of heating and hot water.
• Pressure Maintenance: An intelligent filling system keeps Boiler pressure stable, reducing the need for manual adjustments.

This Boiler can handle two showers with minimal disruption, provided the mains pressure is sufficient. Its advanced features make it a dependable Boiler for homes with higher water demands.

Vaillant ecoTEC Plus 838

Vaillant’s ecoTEC Plus 838 offers excellent performance for dual-shower households.

Key Features:

• Flow Rate: Delivers up to 15.9 litres per minute, making it ideal for simultaneous shower use.
• Modulating Burner: Adjusts power output based on demand, improving efficiency and reducing wear and tear.
• Quiet Operation: Runs quietly, ideal for family homes.
• Compact Design: Fits in standard kitchen cupboards for space-saving installation.

This Boiler’s high flow rate and advanced features make it an excellent Boiler for homes that run two showers simultaneously.

Glow-worm Energy 35kW Combi

Glow-worm offers an affordable yet powerful option with their Energy 35kW combi boiler.

Key Features:

• Flow Rate: Provides up to 14.4 litres per minute, suitable for two moderate-flow showers.
• Energy Efficiency: ErP A-rated with features that help reduce energy consumption.
• Durability: Built with high-quality aluminium for long-lasting performance.
• Compact and Lightweight: Easy to install in smaller spaces.

While it may not have the advanced controls of other brands, the Glow Worm Energy is a reliable and cost-effective Boiler for homes needing dual-shower capacity on a budget.

Viessmann Vitodens 050-W 35kW

Viessmann’s Vitodens 050-W range is a highly efficient, German-engineered Boiler suitable for homes with multiple bathrooms.

Key Features:

• Flow Rate: Up to 14 litres per minute, ideal for two showers.
• Efficiency: Features a stainless-steel heat exchanger for reliability and high efficiency.
• Connectivity: Compatible with smart thermostats for better energy management.
• Quiet Operation: Runs at low noise levels.

The Vitodens 050-W combines efficiency, performance, and a sleek design, an excellent Boiler for running two showers.

Comparison & Summary

The above Boilers offer features that make them suitable for running two showers simultaneously:

• Worcester Bosch Greenstar 8000 Life: High performance and smart technology.
• Vaillant ecoTEC Plus 838: Superior flow rate and modulating burner for efficient use.
• Glow-worm Energy 35kW Combi: Cost-effective and reliable for homes on a budget.
• Viessmann Vitodens 050-W 35kW: Highly efficient, durable and quiet operation.

When selecting a Boiler, consider your household’s requirements, including water flow rate, energy efficiency, and budget. It’s best to consult a Gas Safe registered engineer who will determine the best Boiler for your specific needs.

Alternatives For Enhanced Performance

If your current combi Boiler struggles with two showers, consider the following options:

Upgrade to a Higher-Capacity Combi Boiler

A model with a larger output, such as 38-42 kW, will provide a higher flow rate, making it better suited for homes with multiple bathrooms.

Install A System Boiler & Cylinder

If space allows, a System Boiler with a pressurised cylinder will store hot water and deliver it to multiple taps and showers simultaneously without compromising pressure or temperature. While running two showers on a Combi Boiler is possible, a System Boiler and cylinder will perform better.

Water-Saving Measures

Installing low-flow showerheads or thermostatic mixers (or both) can reduce the demand for your Boiler, which is enough to improve performance. It may allow you to run two showers without needing a Boiler upgrade.

Need A New Combi Boiler Capable Of Running Two Showers?

If you live in Essex and need to upgrade your Combi Boiler so you can run two showers, we can help. One of our Gas Safe registered engineers will inspect your central heating system and recommend a Boiler that meets your heating and hot water requirements while allowing you to run two showers simultaneously. Please contact us to book a free, no-obligation survey and quote.