Negative Head Shower Pumps

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More about Negative Head Shower Pumps

Negative head shower pumps are the right place to look when your gravity-fed system does not produce enough natural flow to start a standard positive head pump. They are used where water struggles to reach the outlet under its own force, so they can help support showers that would otherwise be weak or unreliable. This is often relevant in loft conversions, on long pipe runs, or where the shower head sits at or above the level of the cold water storage cistern.

The key difference is how the pump starts. A positive head pump relies on an existing flow of water before it activates, while a negative head pump is designed to detect demand even when there is little or no natural flow available. As a practical guide, if your available flow is below about 2 litres per minute, a negative head pump is often the type to check first. That is a useful rule of thumb rather than a substitute for assessing the system properly.

Within this collection, you will find inline shower pumps in 22mm size designation, with options associated with both single and twin impeller layouts. In practical terms, that means you can compare products intended for different plumbing arrangements and outlet demands rather than assuming one pump suits every job. Some products in the wider range are described for individual outlets, while others are associated with broader boosting duties, so it pays to match the pump to the part of the system you actually want to improve.

One important buying point is that many negative head pumps are also described as suitable for positive head use where the manufacturer approves it. The reverse should not be assumed. If there is any doubt, confirm whether your system is positive or negative head before ordering, then check the supported application in the product details and manufacturer literature. If your system already has enough natural flow to trigger a pump, you may want to compare Positive Head Shower Pumps or browse the wider Shower Pumps range.

If you are choosing between models, start with the basics: your system type, the natural flow available at the outlet, whether you are boosting one feed or more than one, and whether the pump is for one shower or a wider part of the property. Once those checks are clear, it becomes much easier to pick a negative head shower pump that matches the job with confidence.

Understanding Negative Head Pumps

When To Use A Negative Head Shower Pump

Diagram showing when your water outlet will be in positive or negative head

When to use negative head pumps is an important consideration for homeowners and professionals alike. These pumps are not always the answer, but they do a few specific use-cases. We'll discuss these in more detail here:

Scenario 1: Your Outlet is in Negative Head

The old housing stock in the UK was designed to transport water around your home using gravity. However since we've developed our properties and started using water in different ways, we often find the flow isn't powerful enough. The problem that most people experience is that their water outlet is above the line of Zero Head (see diagram). In this case, gravity has no power over your water, so you will have no flow. A negative head shower pump solves this issue by creating a vacuum to suck your water upwards.

Scenario 2: Your Flow Rate is Less Than 2 L/m

In complex systems, sometimes you may not be in negative head, but still the flow rate will not be enough to trigger a positive head pump. It could be a lonely outlet on the other side of your home, or the result of bad or old plumbing design. In any case, a negative head shower pump will again use a vacuum to pull a good flow of water through your pipework to your outlet.

How Do Negative Head Shower Pumps Work?

Negative head pumps create a vacuum to draw water from the tank. Once the water is drawn, the pump boosts its pressure and feeds it to the outlet. Unlike positive head pumps, which require a certain flow rate to start, negative head pumps can start even without any existing flow.

Types of Negative Head Pumps

There are two types of negative head shower pumps, depending on your requirements:

Single Impeller Negative Head Shower Pumps

In the instance that you only need to boost you hot or your cold feed, you will need a single impeller pump. An example of this would be boosting only the hot feed to a bathroom in a Gravity Hot Mains Cold household. Alternatively, if you have an electric shower (in negative head) that is limited by low water pressure, a single impeller negative head shower pump would be ideal for this.

Twin Impeller Negative Head Shower Pumps

When you are looking to boost both your hot and cold feeds, a twin impeller pump is your solution. This could be to used to boost a mixer valve, a mixer tap or an entire bathroom that is in negative head.