FEATURESTORY
by Andrew Taylor
Flushing Hydroponic Systems to Remove
Harmful Salts
F
lushing hydroponic systems is done to re-
move deposits of general dirt, salt precipi-
tates and algae from the root zone, medium
and other system parts. Pay particular at-
tention to flushing the root zone and feed circuit.
Inspect filters, inlets and feed outlets prior to re-
plenishing the system with fresh nutrient. These are
prone to becoming blocked with solid material dis-
lodged during the flushing process.
Recirculating System Guidelines
Flushing should be done immediately after
the nutrient is discarded. First, do any necessary
manual cleaning, such as removal of any obvious
deposit build-up. Then partly fill the reservoir with
fresh water and operate the pump to flush the feed
circuit, medium and root zone. Flushing can be en-
hanced by spraying the system with a garden hose.
Discard the waste, and then repeat the process until
the waste water is clear and its conductivity is equiv-
alent to that of the make-up water.
Run-to-Waste System Guidelines
Although it is relatively common for hobbyists
to flush their system every 7-14 days, some com-
mercial growers consider it necessary to flush daily.
The frequency ultimately depends on factors such
as salinity, temperature, medium, plant variety and
general management practices.
If flushing can be scheduled to occur when the
nutrient reservoir is empty then the existing system
hardware can be used. Place low alkalinity* water
in the reservoir and operate the nutrient pump until
the EC of the run-off water is no higher than ~0.5mS
above that of the water in the reservoir. It can be a
benefit to do additional flushing with a garden hose
if the surface of the medium is readily accessible.
If the nutrient reservoir cannot be emptied to
conduct flushing, it will be necessary to have an-
other dedicated reservoir and pump for flushing (Fig
12.2). This can be connected to the existing feed
circuit at a junction controlled by a 2-way valve.
The valve is simply diverted to the second reservoir
whenever flushing occurs. GG
* Lower the pH of tap water to ~5.0. RO or rain
water will not need adjusting.
Andrew Taylor is the Chief Chemist at FloraMax. You can
visit their website at Floramax.com.
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June 2018
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