Liquid follows the path of least resistance, which doesn’t always play into your water storage plans. Whether it’s rainwater, greywater, sewage or some other type of liquid, you have to be mindful about how everything will flow. The wrong pressure can stagnate the system or even send it backwards! Poor pressure is also an annoyance if you rely on a water storage system for irrigation, taps, cisterns and other outlets.
Sometimes these issues can be resolved by gravity, but in other cases a pump is the way forward. How can you choose the right fit for your water works? Let’s look at four things to know about pumps:
Pump vs. Elevation
Pumps exist mainly for pressure. Water will go wherever pressure pushes it, so pumps direct water by changing the pressure. When deciding if and where you need a pump, look at where you need pressure. But it may not be about just getting water to the right place. Some appliances, such as washing machines, need the correct water pressure in order to work.
Start with the elevation of your main storage tank. You may have noticed that many tanks, such as on farms, are kept high above the ground. This is to up the water pressure – roughly 0.1 bar per meter of elevation. So a tank 4 meters off the ground can provide around 0.4 bar of pressure. But to place a tank that high will require a special and well-anchored structure. If you can’t elevate the tank, a pump can be used to add pressure. Of course, if you do not elevate the tank, you’ll likely need a pump to move water into it.
There is a second reason for using a pump: it can direct water when you need it. For example, an appropriate pump can detect if your tank is running low and thus switch to a different tank or the municipal mains. But if you intend to connect such a system to your building’s plumbing, it is required to use a qualified installer. This is not only for the plumbing, but also the electricity your pump uses to operate.
The wrong pressure arrangement can severely damage your plumbing and devices connected to it. It can also cause unsavoury problems such as backwashing – something you never want to experience with a sewage line or septic tank. In addition, water is heavy. At a kilogram a litre, even a small tank can weight several hundred kilograms when full. If the structure underneath – soil, a concrete base or a metal frame – is not vetted to handle this, the results can be devastating. More than one house has flooded because a water tank collapsed.
Types of pumps
Pumps come in many sizes and for many uses. It is important to understand your requirements beforehand. This includes tank placement and elevation, but also factors such as the number of taps to be fed . Some pumps are installed outside of the tank and some are submerged into the liquid. At Calcamite we design tanks for both, as well as modular compartments for built-in pumps.
All pumps need an electric power source, such as mains or a generator. Some pumps have built-in pressure switches and flow sensors to ensure that the water supply is uninterrupted. They can detect changes in the system, switching on at the right time to ensure uninterrupted delivery of water. Such features can also be added with pump accessories or companion devices. A resilient pump should have fail safes against dry-running and reverse pressure: a pump is often the guardian of your system, protecting it from any unexpected liquid moving in the wrong direction (such as storm water flooding the pipes).
Pumps need to be maintained, but how easy that is will depend on the use case. A pump operating inside a septic tank should ideally not need a lot of regular attention, and a pump that sits outdoors should be resilient or protected against the elements. Complying with the right specifications of a pump will ensure a long life – not doing so will cause lots of headaches.
Pumps have both filters and electric components that need periodic inspection and maintenance. This varies depending on the pump type and model. Be aware of how frequent this is and how demanding it may be. A hard-to-reach pump that needs attention every month is not going to make anyone happy. Don’t forget about the tank itself: leaves and other debris caught in a tank can lead to blockages and the more frequent replacement of filters.