PUMP USAGE IN RAINWATER RECOVERY

Rainwater collected on your roof doesn't just find its way into your consumption points. To get the water from your cistern to indoors, you use a pump. However, there are different types and sizes. So, the search for the right pump for your rainwater system is often one where many questions arise. The right kind of pump, the placement, how powerful the pump should be or which extras you should be purchasing. At SmartWaterLoop, we are happy to give you independent advice from our extensive knowledge and experience. Based on that advice, we can guide you to the purchase and placement of the right pump for your project, if desired. Sustainable water management without worries, that's what we stand for! Do you still have questions after reading or are you ready for action? Contact us

Where do you place which type of pump? The difference between hydrophore pumps and submersible pumps

A first factor to think about when installing a pump is this: which type do I choose and where am I going to place it? Well, where you place it depends mainly on what type of pump you choose. In terms of pump types, there are two possibilities that are recommended in Flanders by the Flemish environmental department[1]: Submersible pumps and Hydrophore pumps.

An Immersion Pump is placed directly into the cistern and thus always remains in the water. Submersible pumps are often a practical option, as they automatically suck the water out of the well through a suction hose with filter and a float ball hanging from the pump[2]. This float contact automatically shuts off the pump if the water level in the well is too low. Since submersible pumps are in the well and under water, there is no noise pollution[3]in your home. Submersible pumps are often made of stainless steel and therefore usually slightly more expensive[4]. However, they are also quiet, reliable, and robust.

A Hydrophore pump is placed indoors in the basement or a storage room. They are self-priming and turn on and off automatically, maintaining the same water pressure in your piping system. To make this type of pump work smoothly with your rainwater system, a pressure regulator is often installed along with it. These pumps are generally less expensive than submersible pumps butcanproducenoise sometimes. Modern, more expensive hydrophore pumps already operaterelatively quietly, but if you have poor acoustics in your basement or storage room it can certainly generate some noise. Hydrophore pumps are technically a bit more complex, making them a bit less robust.

What if you run out of rainwater? The difference between refill kits and transfer systems

It can sometimes happen that during long periods of drought your cistern becomes empty, and you can no longer count on your free rainwater. Fortunately, there are solutions for this, which can be integrated into your pumping system. Both the system and its connection must be approved[8] by an authorized inspector.

A first option is a refill system (see image) with which you refill your empty cistern a little bit with tap water. An important obligationthe Flemish government prescribes is that your rainwater system may never be directly connected to your tap water. This can cause contamination and introduce bacteria or other contaminants into your drinking/shower water[7].This system requires an additional fill line to the tank.

refill system with wich you refill your empty cistern — refill system[9]

A second option is a switchover system (see photo) with a buffer tank that automatically switches to tap water when your rainwater runs out. The big advantage is that you don't have to place an extra refill line to the tank. On the other hand, it increases the standing time of the residual water in the tank, making the water slightly less "fresh" when it is then brought in again from the cistern. In this case, additional filtration is definitely something to think about. See "link to blog about filters"

switchover system that automatically switches to tap water when your rainwater runs out — switchover system

What is pump flow and head? Reading the pump curve and sizing correctly

A third consideration when buying and installing a rainwater harvesting pump is the difficult choice between the technical aspects of many models. This is important to ensure that your indoor and outdoor water consumption points can also function properly. Two performance characteristics are key, and every submersible and hydronic pump has a specification for both parameters, namely maximum flow rate and maximum head.

This characterization is often very confusing: at maximum flow rate there is no head and at maximum head there is no flow rate. Thus, these parameters are not useful in a direct manner. Therefore, all intermediate combinations of flow and head are also included in a pump curve, so you can determine which levels you need.

The flow rate of a pump is usually expressed in m3/h or l/s. This parameter measures how many cubic meters (or liters) can be pushed through the pump per hour (or second). Powerful pumps have higher flow rates, often around 5-6 m3 /h, but usually a lower flow rate is sufficient. Let's look at some examples: · refilling a 6-liter toilet cistern in 1 minute takes 0.1 l/s or 0.36 m³/u · A washing machine or pressure washer uses 10 l/minute or 0.6 m³/h · Using a garden hose or irrigation sprinklers takes up to 15l/min or 0.9 m³/h

The head or discharge pressure of a pump is usually expressed in meters or in bar (1 bar =~10 meters). This parameter describes how high the liquid can be pushed up and is equivalent to how much pressure can be built up in the pipe system. Most rainwater recovery pumps have a head between 35 and 65 meters (3.5-6.5 bar). But how much pressure do youactually need? Again, let's look at some examples:

For a toilet flush of 0.36 m³/h, the pressure loss is influenced by the pipes, for 20m of pipe with inner diameter 12mm this is 0.2 bar.
For a washing machine, the minimum supply pressure is 0.5 - 0.9 bar, to be increased by the pressure loss across the pipes. For 20m of pipes, this is an additional 0.5 bar.
The minimum supply pressure for irrigation sprinklers is 1.5 bar, to be increased by the pressure loss across the pipes. For 20m of pipes, this is an additional 1 bar.

The higher your pump must push the water, the lower the flow rate becomes. This relationship can be read on the pump curve, which describes the trade-off between flow and head. The graph to the right shows an example.

Why is proper dimensioning of pumps important?

If the pump is undersized and there is not enough pressure or flow, some appliances such as washing machines or irrigation sprinklers do not work properly or fail. This can also happen when multiple consumers become active at the same time (e.g., toilet flushing when washing machine is running).
A pump with a high flow rate and head is generally larger, heavier, and significantly more expensive.
If the pump is oversized, it creates a lot of unnecessary pressure in your pipes. This pressure increases the risk of leaks on the one hand, but the excess pressure is also converted into heat and thus an energy loss develops. It seems unlikely, but in many current rainwater systems, up to 5 times more energy is consumed than necessary.

How long does a pump last and is maintenance required? Life span, impact, and maintenance

Naturally, you would like your pump to last a long time and require as little tinkering as possible. Depending on the type of pump, its location (indoor/outdoor) and the desired flow rate/head, the cost will vary, but also its lifetime and possible maintenance costs are important variables.

Generally speaking, the lifespan and reliability of rainwater pumps (that are produced in good quality) can last 10-15 years without worry, as long as the flowing water remains fairly clean. Pumps with electronic components (sensors, controllers, pressure regulators) are slightly more susceptible to failure or breakdown of these components, but usually these are easily repairable by replacing the faulty item. The main pumps themselves are quite sturdy and if they fail, it is often more of an electrical issue (capacitor, short circuiting in wiring) and not always easily repairable. Additional measures such as surge protection on your electrical system and a properly sized expansion vat connected to the piping system can significantly increase service life.

When it comes to maintenance, it is important that you clean the intake filters and cistern often enough. More information on cleaning these components can be found in our information sheets on cisterns and rainwater filters. Submersible pumps are slightly more difficult to maintain compared to hydrophores, partly due to their arrangement in the water which makes accessibility difficult. If you make the mistake of buying an oversize pump it also might be too heavy to easily pull out. It is also necessary to clean your suction kit regularly to make sure it is not clogged! Specifically, how can SmartWaterLoop help me? The right pump choice clearly requires some research and expertise before an optimal decision can be made. Fortunately, with our Smart Water Calculator we take all these parameters into consideration and review them tailored to your project and your budget! If you want to know how this calculator works, click here! Interested? Be sure to contact us!

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PUMP USAGE IN RAINWATER RECOVERY

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