Automatic Backwash Sand Filter for Drip Irrigation System

When it comes to drip irrigation filters, many people immediately think of simple mesh models - and this is the main mistake I encounter in the field. Sand filters with automatic backwashing are not just a “more advanced version”, but a fundamentally different approach to emitter protection. In practice, the difference is visible after the first season: where conventional filters were installed, blockages and uneven watering begin, but our systems with automatic flushing work for years without intervention.

Why automatic washing is not a luxury, but a necessity

Last year we installed the system in the Krasnodar region in an area with high water turbidity. The customer initially wanted to save money and install manual filters. I convinced him to try the automatic option only after showing data from a similar facility: there the maintenance staff simply did not have time to wash the filters manually every 4-6 hours, which led to constant downtime. The automation itself monitors the pressure drop and starts the cycle when it is really needed - sometimes once a day, sometimes three times, depending on the load.

By the way, an important nuance that is often missed: automatic backwashing should be done with sand filler, and not with a mesh element. Sand retains not only mechanical particles, but also organic suspensions, which simply stick together in lumps in meshes. We tested it at a facility in the Rostov region - after switching from mesh filters to sand filters, the number of emitter cleanings decreased by 70%.

Another point is the quality of the sand itself. You can’t take the first quarry one you come across - only filter quartz with a certain granulometry. We cooperate with Shandong Linyao Intelligent Agriculture Technology LLC precisely because they supply proven components, including fillers. On their website www.lyzhihuinongye.ru there are detailed specifications for fractions - a trifle, but critically important.

Design features that affect performance

The filter housing is always reinforced fiberglass or stainless steel. Plastic does not withstand constant pressure cycles when flushing, this has been proven through bitter experience. In 2020, we tried to install polypropylene housings, but after a season microcracks began to appear and we had to completely change the system.

The distribution system inside the tank is where the main difference between budget models and professional ones lies. Good collectors distribute water evenly during filtration and create turbulent flow during flushing to lift up all the sediment. Cheap analogues simply do not wash away the sand around the edges - dead zones are formed where bacteria accumulate.

Solenoid valves - I recommend installing them with a manual override. At one of our facilities in the Stavropol region, the controller burned out, and the system stopped working for a day while a replacement was being transported. Now we always design with the possibility of manual control at critical nodes.

Integration with general irrigation system

Automatic Backwash Sand Filternever works on its own - only in conjunction with pressure controllers and a control system. We usually install sensors before and after the filter to accurately monitor the moment for washing. If you do it on a timer, you will either rinse in vain or miss the moment of clogging.

For large systems we often use a cascade scheme - several filters work alternately so as not to create pressure dips in the line during flushing. The technology has been tested on projects of Shandong Lingyao LLC - they specialize in complex “turnkey” solutions, where filtration is part of a single hydraulic structure.

An interesting case was in Crimea: there they had to combine sand filters with disk prefilters due to the high algae content. Sand handled sand and silt, but discs held organic matter better. Such hybrid solutions are often required on open water bodies.

Typical installation and operation errors

The most common is incorrect strapping. The filter must be positioned strictly horizontally, otherwise backwashing will not occur evenly. We mark the site with a laser level - it seems like a small thing, but it affects the efficiency.

They forget about a drainage line of sufficient diameter - when flushing there is a powerful flow of dirty water, if the pipe is narrow, back pressure is created and the sediment is not completely removed. Minimum DN50, or better DN65.

Saving on shut-off valves - installing ball valves instead of gate valves is a mistake. During an emergency shutdown, the valves shut off the flow more smoothly and there are no water hammers. We repaired a system where, after abruptly closing the tap, a pipe broke - the repair cost more than all the savings on fittings.

Prospects for technology development

Now we are testing a system with water turbidity sensors - they send a signal to the controller until the pressure drop increases. This is especially true for sources with unstable water quality, for example, after rains.

Smart filters are already able to transmit data to monitoring systems - this is convenient for remote control of large agricultural enterprises. The website www.lyzhihuinongye.ru has examples of integration with their platforms for smart agricultural parks.

We are thinking about recycling the wash water - for now it is simply dumped, but in arid regions this is wasteful. We are planning to test a system for settling and returning to the main reservoir - it is technically difficult, but it can pay off where every cubic meter of water counts.

Selection of equipment for different conditions

For small areas up to 5 hectares, one filter with a 600-800 mm tank is sufficient. Above is a cascade of two or three devices. It is believed that one filter can serve up to 15 hectares, but this is with ideal water - in reality it is better to keep a reserve.

If the water has a high iron content, aeration columns are needed before filtration, otherwise the sand is quickly cemented by oxides. There was a sad experience in the Lipetsk region, where the filler had to be completely changed after six months of operation.

Temperature conditions - in winter it is necessary to drain the system. Even in the southern regions there are frosts that break the hulls. We install automatic drain valves at the lowest points - cheap and reliable.

Overall, automatic sand filters are a case where the initial investment pays for itself many times over due to reduced operating costs. The main thing is not to skimp on key components and correctly integrate them into the overall system. As practice shows, it is better to set up high-quality equipment once than to constantly struggle with the consequences of simplified solutions.