CLEANING THE POND
After 4 years of basically maintenance-free operation, a strange
phenomenon began to occur. I noticed that the flow of water over the
falls was gradually getting smaller. I found that if I turned the
filter off for a minute or so and then restarted it, the flow
increased
again. I figured that perhaps there was some junk building up in the
impeller of the pump and when I turned the power off, the water
would
flow backwards through the system and push the debris out of the
impeller.
At one point I even took the pump apart and cleaned the impeller out
by
hand. But there was hardly anything there.
However, the problem gradually got worse and I had to turn the pump
off
on a more and more frequent basis.
Then I finally figured out what was really going on.
On top of the 2" filter material on the bottom of the pond, I had
placed a very tough layer about 3/16" thick of a kind of weed
barrier
material. The idea of this was to protect the filter material from
debris and I had attached nylon cord to this stuff so I could lift
it
out and clean it if necessary. All the water for the pump is drawn
through this material on the bottom of the pond and it seems that
this
top layer had finally clogged up with debris. So the pump was
working
harder and harder to draw the water through this stuff, eventually
finding that it couldn't get enough water for a full flow.
So I decided it was time to clean the system.
Because I used to do a little scuba diving, I decided it would be
fun
to rent some gear for a weekend and swim with my fish. This would
also
mean I could take the time to carefully inspect the state of the
filter
material and network of pipes underneath to see how they had fared
over
the 4 years. And I hoped it would also allow me to work under water
more slowly with less disturbance to the fish.
Getting the barrier layer out of the pond wasn't as easy as I'd
hoped.
It was covered with slime, weed roots and heavy with water.
However, by rolling the sheets up into manageable sizes, I managed
to
heave them out of the pond.
I must say how great it was to just be in such close proximity to
the
fish. They were very tame already and so they would be just inches
away
from my face where I could really watch and appreciate them. I took
some time to just relax and enjoy hanging out in their world for a
while.
After removing the 'weed barrier' layer, I was happy to see that the
pump ran with great volume and quickly cleared up the water after I
disturbed it with my activities.
Now I'd gone this far, I wanted to look at the filter material
itself,
and also the pipes underneath.
Removing the filter material really was a breeze .. certainly would
not
have needed the scuba gear of course, but it was fun to work with
it.
The filter material, unlike the heavy barrier stuff, easily sheds
the
water if you lift it slowly out of the pond. I passed it out to a
friend from inside the pond with no difficulty. The only issue was
whether to let all the water drain out along with the fine debris
that
came with it, to cloud up the pond. So we drained enough that we
could
easily lift it out, then lifted it out with as much water and debris
as
we could.
Once out of the pond I used a pressure washer to clean up the
material.
The stuff itself is practically indestructible and cleaned up very
well, as you can see from the picture.
Once the filter material was out, the pipe manifold on the bottom
was
easy to access.
I wanted to see the condition of the pipes on the insides, so I took
a
couple of them apart. I had not glued them in place originally, so I
could adjust them or clean them later. There seemed no need to glue
them as they are a tight fit anyway and the pump suction tends to
pull
them
together rather than push them apart.
If you look carefully at the picture below, you can see where the
exit
pipe on the bottom (green) comes up the side of the pond (there's a
white section). It then goes up over the side of the pond (covered
by
flagstones) then down
underground again and runs to the pump in the little pump house
directly behind the pond, with it's hinged roof open. The pump is
below
the waterline level so once
it's primed, the water automatically feeds the pump by gravity.
I found that there was quite a lot of very fine silt in the pipes,
so I
figured I might as well clean them out while I was at it. I debated
rigging up some kind of vaccuum system to suck out the stuff, but in
the end, I decided to just take the pipes apart, lift them out and
clean them up out of the water. The pipes are 3" in diameter and
have
holes in them in two rows. It was a bit messy but once I got the
hang
of it I found if I moved slowly I could get them out without too
much
disturbance. Then I emptied out a tasty 'sausage of sludge' from
each
one
which I used in the garden.
Replacing the filter material was quite straightforward as it's so
wonderfully light and easy to work with. I just floated the sections
on
the top of the water and then gradually submerged them as they
became
waterlogged. Then I could move them into position and secure them
with
a few pieces of slate.
Because it was so darned easy to work with the filter material, I
decided not to try to replace the layer of screen material that I
had
used in the beginning to protect the filter material. That was what
got
clogged up after 4 years, whereas I can't imagine how the filter
material itself could ever clog up like that.
Now imagine trying to clean out an undergravel filter in the bottom
of
the pond that used real GRAVEL, instead of this filter stuff!
Probably
have to move the fish out, drain the pond and get a back hoe. A
reely
reely big, heavy and dirty job compared to this.
I could easily have done the job without using the scuba gear ..
that
was just to have a bit of fun and maybe it made it a little easier
to
work slowly.
It's now 2009 and the system has been working with no maintenance at
all for three more years. There are a lot of water weeds (see below)
now growing
from the bottom and I have left them in because the fish seem to
like
swimming in them, they use them for laying eggs and it gives some
protection against the heron and the sun. And I've kind of come to
like
them. However, I am wondering how far the
root systems have grown into the the filter material. The weeds are
easily pulled out but would probably leave their roots behind. But I
know I can always lift out the filter sections and give them another
clean if I have to, with relatively little fuss.