bio-10.pdf

Construction of Automatic Bell Siphons for Backyard Aquaponic Systems

Following is a brief outline for dealing with some of
the most common problems and issues that have been
encountered with new bell siphon construction. It must
be stressed that this is not by any means an exhaustive
guide to bell siphon construction, and any project involving
water and live animals requires significant attention
and care.
Problem: The bell siphon will not start; the water level
in the grow-bed remains high and does not flush.
Solutions:
1) Check the seal around the snorkel where it enters
the bell, or the seal connecting the cap to the bell
pipe. These two seals must be airtight, otherwise the
vacuum that initiates the siphon action will not form.
2) Ensure that the bell siphon and gravel guard are firmly
in place at the bottom of the grow-bed. Pieces of cinder
or gravel may move under or through the gravel guard
and come to rest between the teeth and tank bottom,
causing the space between the bell and standpipe to
expand. This added space can prevent the siphon from
starting or interrupt its operation in other ways.
Problem: The bell siphon will not stop; the water in the
grow-bed remains very low, water is constantly trickling
out of the drain, and the tank does not fill back up.
Solutions:
1) Check the snorkel for obstructions. If the opening of
the snorkel is pinched or blocked by cinders or biological
material, air will not be able to move freely
through it to break the siphon. Clear the snorkel, lift
the bell siphon out of the grow-bed to manually break
the siphon, and then replace it in the gravel guard to
continue the cycle.
2) Check the height of the snorkel tube opening. If the
snorkel tube opening is too low (i.e., too close to the
teeth), it may not provide enough air injection to break
the siphon. Try cutting the snorkel tube slightly shorter
and see if it works. Repeat this step if necessary, as
this is a common solution to this issue.
3) Adjust the drain. Try different combinations of pipe
lengths between the 90° elbow fittings on the underside
of the grow-bed. Often a slightly longer or shorter
vertical or horizontal drainpipe can fix the problem
with no other alterations.
4) Check the incoming flow rate. If the rate of water flow
coming into the grow-bed is too great, the siphon will
have difficulty draining the tank. This is rarely the
cause of the problem, but it is worth investigating if
all of the above solutions do not work.