11
10
Degassing the Filter Media
Degassing is part of the normal filter maintenance procedure. In some situations, the
surface of the filter media may appear clean, but there is low flow. This is an indication
the filter media is air locked. This may be due to accidental de-watering of the filter or
the presence of dissolved gases (hydrogen sulphide, carbon dioxide, air, methane) in
the raw water source. Air locking in the filter bed will cause a reduction in the flow rate
through the filter. Remove the trapped gases from the filter media using the following
procedure.
Step 1.
Close the filter inlet valve and outlet valve.
Step 2.
Remove the filter float assembly at the union connection and remove the
diffuser basin to view the top surface of the sand.
Step 3.
Connect the CIP hose to the CIP reverse flow valve downstream of the pump.
Open the valve to ensure that the flow rate restriction device is limiting the flow rate to
approximately 4 litres per minute to prevent damage to the filter media. Connect the
other end of the hose to the lower valve on the filter standpipe (figure 9-2). Open both
valves on the CIP hose and dispel any air in the line through the anti-siphoning valve.
Close the anti-siphoning valve.
Step 4.
The water will slowly enter the filter from the bottom, expelling any trapped
gasses through the filter surface. Continue to bottom fill the filter until you don’t see any
more air bubbles surfacing. Be sure to run this for a minimum of 15 minutes to ensure
all gas pockets are filled with water. Periodically tap the sides of the filter during this
process. Drain excess water through the maintenance drain.
Step 5.
To restart the filter, close the filter maintenance drain valve, the CIP reverse
flow valve downstream of the pump and the lower valve on the filter standpipe.
Step 6.
Replace the diffuser basin. Re-attach the filter float assembly. Open the anti-
siphoning valve and the outlet valve.
11
Winterization
Do not allow the filter system to freeze when it is filled with water. Winterization
consists of the following steps.
Step 1.
Perform a complete maintenance cycle on the BioSand Water Filter as
described in Section 9.
Step 2.
Unplug the pump.
Step 3.
Turn off the water supply and drain the filtered water storage tank and the
plumbing system. Make sure all water is drained from the pump head. (See the pump
manufacturer’s instructions.)
Step 4.
Close the outlet valve and anti-siphoning valve.
Step 5.
Undo the hose from the lower valve on the filter standpipe. Slowly drain all of
the water out of the sand bed using the standpipe lower valve.
