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,lasts. The outlet pressure shOuld therefore be only
in“ excess
of that required. If the rate of descent is very high
inside the
drum“ may become so pressurised that it breaks the water seal
,
leaks to the atmosphere. The trick is to weight— the‘ drum just
sufficiently so that it descends into the hole at a rate which just
_
provides enough air to run the required appliances. Repositioning
of the drum
at the start position is easier if a large hole can be
temporarily opened in the top to admit air quickly. This systemis ‘
admittedly' rather ‘way out’, and troublesome to install, but if
Correctly 'used it can run a fair‘number of appliances with only daily
î
__recharging, and it does demonstrate what a little thought and enter—
prise can achieve;
'
_
WATER FELTERS
j
F ilters for aquaria come “in all sorts of shapes, types and sizes, but
they all perform the same basic function, and that is to circulate the
—'
water through some form of straining or cleansing medium at such
a
rate
that the water is kept clean and sweët. There are various
,
Categories into which filters can be grouped, such as ‘inside’, ‘outside’
.
and ‘sub—gravel’, but the situation of the filter is
nearly as im__
as the way in Which it operates.
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