Existing Clogging Problems

Diagnosing the clogging problem

Clogging problems in microirrigation systems are usually diagnosed by either (1) the operator noticing that some emission device(s) have stopped operating or (2) an emitter evaluation (discharge collected from a sampling of emitters) being done with the results indicating partial or total clogging of emitters.  With an indication that there is a clogging problem, determining the cause of the clogging is important in determining the best corrective measure.

The following is a list of steps that may be taken to provide information on the source of emitter clogging:

1. Flush the lateral lines, running the flushed water through a nylon stocking or a paint straining cloth (available wherever paint is sold).  Examine the material collected on the nylon or paint strainer.  If it is primarily mineral particles, that may be the cause of your clogging.  You should expect most clay and silt size particles to pass through the filters, with some of them settling out in the lateral lines.  A stream of flush water that stays dirty for several minutes before it runs clear is an indication that too many particulates may be getting past the filters, causing emitter clogging. Click here for more information on flushing microirrigation systems.
   
   
2. Try to determine if there is any pattern to the emitter clogging.  If most of the clogged emitters are at the end of the lateral lines, this often indicates particulate clogging since the particulates are settling out at the ends of the laterals where the flow velocity is the lowest.  This type of clogging can often be prevented by regular line flushing. Click here for more information on particulate clogging.
   
   
3. Open the end (or disconnect the head of a lateral line) and feel with your finger to see if the inside of the tubing is slimy.  Also check the flush water from lateral lines for evidence of organic matter.  If it appears that there is biological contamination in the system, that may be the source of the clogging. Click here for more information on biological clogging issues.
   
   
4. Inspect the emitters and take note of the condition of the soil directly around the emitters.  If there is evidence of a white, crusty material (lime = calcium carbonate) or of a reddish staining (iron), chemical precipitation may be causing your emitters to clog.  The calcium carbonate will fizz and disappear if put in contact with a strong acid.  Iron will disappear overnight if left in contact with a strong acid solution. Click here for more information on chemical precipitate clogging.
   
   
5. Check the backwash water from sand media filters or examine what is being caught on screen or disk filters to provide an insight into what contaminates may be clogging the emitters.  If the filters are collecting a large load of organic matter, that can give you a clue about the clogging source.  Chemical precipitates on the filters (e.g. reddish staining from iron on screen filters) may indicate that chemical precipitates are the cause of the clogging.

With sand media filters, you may find it useful to open the access/inspection port when the system is not pressurized so you can examine the sand.  The condition and "feel" of the sand may tell you whether there is an organic/slime problem in the system or if there are excessive fine particles in the system.  This is also a good time to see if the sand needs replenishing (sand level too low) or replacement (sand is “smooth”, like beach sand – particles of filter sand should have “sharp” edges).  Also make sure there are no large cracks in the sand that would allow water to bypass the sand and flow directly into the underdrain system.

If none of this helps you diagnose your clogging problem, you may find it useful to return to the section Prediction of Clogging Problems.  There you will find information on testing your water to determine whether you need to be watchful for drip emitter clogging.