Backwash the sand filter system

There are different filter systems to purify a fluid like water. One often used system is the sand filter system. Like any other filter system, the sand filter system must be maintained and cleaned. In the sand filter system that is the backwashing. Below you will find instructions on how to backwash a sand filter system.

Construction of sand filter systems

In order to be able to operate the sand filter system correctly, it is first of all important that you know the individual important components. Of course, there are also simpler sand filter systems than the one shown below. But the principle of operation during backwashing is the same:

  • Circulating pump (two directions of running)
  • pressure gauge
  • Multi-way valve (four-way or six-way valve)
  • Inflow and outflow from the water basin (runs over the multiway valve)
  • Connection to the pump and drain to waste water (runs through the multiway valve)
  • filter vessel

Construction of the filter boiler

The interior of the filter housing looks like this (from top to bottom):

  • water distributor
  • Sand layer or several sand layers (different grain size)
  • Standpipe extending from the distributor to the filter star)
  • Filter star or filter cross with nozzles, pins or candles (which absorb the filtered water)

Function of the multi-way valve

But also the multi-way valve is important in its function, as it can be adjusted. Depending on whether it is a simple valve (for example, a sand filter for wells) or a four- or six-way valve, you have various additional functions:

  • Close the complete system (pressure is built up and displayed via the pressure gauge)
  • Circulate for filtering: the system is open in the filtration direction from and back to the pool
  • Backwashing: the system is open from the pool to the sewer / sewer connection (against the filtration direction)
  • Rinsing: the system is open from the pool to the sewer / sewer connection (in filtration direction)
  • Draining: from the tank directly to the waste water connection (without running through the filter tank)
  • Circulating for another reason: return from the pool to the pool without filtering, for example for heating

On and off switching and pumping direction of the circulation pump

Depending on what you plan to do, you can move the multiway valve to the appropriate position (manual or motorized). In addition, you can also switch the circulation pump on and off, as well as switch on forward or reverse here at power. For all functions such as circulation, emptying or rinsing, the pump must be set to regular flow. When backwashing, however, opposite.

Always switch off the pump before operating the valve!

It is also extremely important to turn off the pump before operating the multiway valve. The pump must not run if you want to change the multi-way valve! Otherwise, this is a typical situation, such as sand from the sand filter system in the pool or in the multi-way valve device. While the sand in the tank is just annoying, it can destroy the mechanics as well as the seals in the valve.

Instructions for backwashing

Now, the filter is cleaned by backwashing. If you change the running direction of the water through the filter, but then open the inlet to the wastewater, it flushes all the dirt collected in the filter sand from the boiler. As dirt and sand get into the pipe system and the valve, backwashing consists of two steps:

  • backwash
  • rinse

When backwashing the water runs upside down through the filter. When rinsing then normal, but not in the basin, but also in the drain. For example, purged sand is flushed back into the filter vessel during backwashing into the piping and the multi-way valve. It therefore ensures, above all, that the functions of the returnable valve are retained and that sand can not get into the tank in the short term.

Tips & Tricks

The backwash instructions we publish here are general. However, there are small differences between the different sand filter systems. Thus, the operating principle during backwashing may differ slightly. As with your sand filter system backwashing works exactly, please refer to the instructions of the filter manufacturer.

More about the control of sand filter systems can be found in our series of sand filter systems. In addition, we offer numerous other guides and articles for maintenance, as well as how you can build a sand filter system yourself.

Video Board: How To Backwash and Clean Above Ground Sand Pool Filter