Spa Filtration: Suction vs Pressure - Which is Better?

Thinking about which type of filtration system is best for your spa pool? Wondering whether suction filtration or pressure filtration is more effective? If yes, then this blog is for you!

The filtration system in a spa is designed to filter out dirt, debris, oils and scum from your spa water. There are two main types of filtration systems used in spas: suction and pressure.

In this article, we will discuss in detail the differences between suction and pressure filtration systems, and help you understand how all the components work in the system.

We'll also cover:

What is spa filtration and why is it important?

Sanitising with chlorine or hydrogen peroxide helps to kill bacteria, but it does not always remove all of the dirt and other particles that can accumulate in the water. This is where a filtration system comes in.

Spa filtration is the process of pumping the water in a spa through filter media to remove dirt, scum, and other debris. Different spa models vary in configuration, but in general, the filtration system consists of a filter and filtration media, circulation pump, suction vent and suction return vent.

The filter is usually made of pleated paper or synthetic fabric that traps contaminants and small particles as water flows through it. Spa filtration is important because it helps to keep the water clean and clear, and it also helps to prolong the life of the spa.

There are a variety of different types of filters available, so it is important to choose one that is designed specifically for use with a hot tub or spa.

How does a suction filtration system work in a spa?

Most modern systems use suction filtration which uses a pump to generate a suction effect that draws water through the filters located in a skimmer into the plumbing of your spa, through the circulation pump, the heating system, any sanitising devices (like UV and ozone), then back into the main spa water.

This continuous cycle helps to keep the water clean and free of contaminants. Suction systems are usually less expensive to operate and maintain than pressure systems.

How does pressure filtration work in a spa?

Pressure filtration systems (also known as vacuum filtration) work by drawing water from the spa or hot tub and forcing it through the filter in a pressurised chamber. The filtered water is then returned back to the spa or hot tub.

Pressure systems are sealed because the filtration draws water out of the main water system into a separate pressurised filter in a canister. Some people believe that pressure filtration is more effective and can reduce the need to drain and refill your spa with fresh water so often.

Pressure systems are typically more expensive to manufacture and maintain than suction systems and are not used as commonly in most modern spas.

What is the suction in a spa or hot tub?

Spa suction is caused by the Bernoulli principle. The hot tub has jets that push water out at high speed. This reduces the pressure in the hot tub.

The surrounding atmospheric pressure is greater than the pressure inside the hot tub. So the water is drawn into the hot tub through the suction fittings. The suction fitting contains a filter that removes dirt and debris from the water as it enters the hot tub.

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How does water circulate in a spa or hot tub?

Without circulation, your spa or hot tub would quickly become a breeding ground for bacteria and other contaminants.

The answer lies in the suction generated by the hot tub's filtration system. This suction pulls water from the spa and runs it through the filter. The filtered water is then pumped back into the spa, completing the circuit.

Depending on your exact spa model, the filtered, heated water is returned to the spa through multiple locations - the 'suction return' vent at the bottom of your spa, waterfall outlet and venturi outlets. Some spa models also return water to the spa through some jets.

This circulation process not only keeps the water clean, but it also helps to distribute heat evenly throughout the spa.

SpaNet® Circulation Pump (blue) and Blower (black)

Is a circulation pump necessary in a spa or hot tub?

A circulation pump is a key component of any spa or hot tub filtration system. Its primary purpose is to circulate water through the filters and heater, keeping the water clean and at a consistent temperature. Circulation pumps also help to distribute chemical treatments evenly throughout the spa or hot tub.

Without a circulation pump, it would be difficult to maintain proper water quality and temperature, making it essential for any spa or hot tub owner. In addition, circulation pumps can also provide massaging action to the jets, making for a more relaxing experience. As a result, circulation pumps are an essential part of any spa or hot tub filtration system.

In a hot tub, water is circulated using a combination of suction and filtration. The hot tub pump pulls water from the tub and runs it through a filter. The filtered water is then returned to the hot tub. This constantly circulating water helps to keep the water clean and also prevents the hot tub motor from overheating.

In addition, the circulating water helps to circulate the heat, meaning that the hot tub will maintain its temperature more effectively. As a result, circulation is an essential part of hot tub maintenance. Without it, the hot tub would quickly become dirty and unusable.

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Do spas filter when the jets are on?

Many people believe that the spa jets and the filtration system are connected, but this is not always the case. Many spa models have a completely separate plumbing line for jets which operates separately from the filtration system.

Some spa models rely on gravity to pull water through the filter, so turning on the jets can actually prevent filtration from taking place.

Other models have a dedicated suction line that pulls water through the filter even when the jets are running.

Still, other spas have a skimmer that removes debris from the surface of the water even when the jets are on. So, if you're wondering whether your spa's filtration system is working while the jets are running, the answer is - it depends!

How many points of suction should my filtration system have?

By law in Australia, a spa must have 2 points of suction plumbed to a pump for safety to release pressure.

What happens if my filters get blocked or clogged?

When the filters in your spa are new or clean, water flows smoothly and easily through the filter cartridge into your plumbing system. There is also a non-return valve plumbed between the filters and the additional suction vent at the bottom of the spa. If the filter gets blocked this valve will open up and get water from the suction so there is enough water available to the pump.

Without this system, the water flow rate would reduce when the filters get clogged, resulting in the pump overworking. Even so, dirty filters in your spa do add extra load onto your circulation pump.

Of course, in this scenario, you are not getting the full benefit of filtration in your spa water. This is why it is important to clean your spa filters regularly and replace them after around 12 months of use.

How do I know if my spa filtration is running?

Your spa is filtering the water in your spa when the circulation pump is running. Most modern spas have an automated system that runs a filtration cycle multiple times throughout the day, so you don't have to worry about it.

If you see small bubbles coming up from the bottom of the spa in the spa, then you are most likely filtering.

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Can I run my heater, jets and spa filtration at the same time?

This depends on a few other factors, such as the size of your heater element and whether you have your spa wired to a 15 amp circuit or a higher current circuit.

If your spa is wired to a lower current circuit like 15 amps, it may automatically shut off the heater while you have your jets running so the system doesn't draw more than 15 amps.

Some spa controllers like the SpaNet® SV series (not SV mini) use a system called 'dynamic thermal turning' which can adjust the output of the heater so it can still operate at a lower current level.

What causes blockages in my spa filters?

One of the most common causes of blockages in spa filters is calcium buildup. This occurs when calcium-rich water (such as from a mineral spring) is used to fill the spa. Over time, the calcium will adhere to the filter media, reducing its effectiveness.

Using cheaper chlorine sanitiser with calcium fillers can also block your filter media much more quickly.

Another common cause of blockages is the accumulation of soap, lotion, and sunscreen residues.

When these products come into contact with the water, they can form a sticky film that traps dirt and other debris. Finally, sweat and dirt can also clog the pores of the filtration system, making it difficult for water to flow through.

To avoid this, it is important to clean your spa filters on a regular basis. The best way to do this is to rinse them with a garden hose and filter wand. If the filters are particularly dirty, you may need to soak them in a filter cleaning solution before rinsing. By taking these simple steps, you can help ensure that your spa filters remain clean and in good working condition.

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In Summary

The filter system is a critical part of your spa pool to help maintain clean water and keep your pumps running efficiently.

The filtration system helps remove dirt, debris, and other soluble impurities in your water, reducing the chances of cloudy or green water!

Suction filtration is the most common type of filtration used in most modern spa pools and swim spas.

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