 fig 2
Hot Tubs | Hot Tub |
As can be seen in Fig. 2, the grids are mounted
on a manifold, 1 the resulting assembly
fits into the tank. A retaining
rod through centre screws into the
base of the tank, and a holding
wheel keeps the is firmly in place.
The top of the tank is held in place
by a clamping ring, the two parts
sealed with a thick O-ring to prevent
any leaking.
The water enters the tank at the
bottom and flows up around the outside
of the grid assembly. It must flow
through the grids, down the stem
cc. each grid, and into the hollow
manifold, after which it is sent
back out of the hot tubs filter.
One partial way to clean this filter
is called backwash, a concept that
we will discuss in greater detail
later. As the term suggests, back
aching means the water is redirected
through the filter in the opposite
direction to normal filtration (accomplished
with a backwash travel, also discussed
below), thereby flushing old DE
and dirt out of he filter.
Not all vertical DE filters are
equipped with a backwash valve to
allow backwash-type cleaning and
so must be disassembled each time
for cleaning. Some are also equipped
for "bumping" rather than
backwashing. In this process, the
dirty DE is bumped off the grids,
mixed inside the tank so the dirt
is evenly distributed within the
DE material, then recoated onto
the grids.
The bumping concept is this: Since
most dirt sits on the outermost
layer of DE (as the DE rests on
grids), there is still relatively
clean, unused DE available beneath.
By mixing DE and dirt together,
somewhat cleaner DE will be brought
to the surface, preventing the need
to actually replace it. Bumping
should only be used as a temporary
filter method, however, since it
is not very effective at cleaning
the filter. In some areas, out of
concern that DE will clog pipes
when the grids are cleaned or backwashed,
local codes require that DE not
be dumped into the sewer system.
In this case, a separation tank
is added next to the filter. When
you are draining or backwashing
the filter, the dirty water is passed
through a canvas bag inside a small
tank before going into sewer or
storm drains. The canvas bag strains
most of the DE out of the water
so it can be disposed of elsewhere.
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