Plumbing

As you can see in some of the earlier pictures the plumbing is in 2 sections.
1. The water from the fish tank to the growbeds and
2. Return water to the fishtank.
The first bit is via a big sump pump which is on the bottom of the fish tank and is connected to the growbeds with 1 and a half inch (40mm) black agricultural polypipe. This is used because I had lots of the poly bits in stock as it is the same pipe we use for all the outdoor plumbing between dams, the bore and header tanks etc. The pump is in a filter sort of bag I had to make to prevent the fish from being sucked into the pump and mulched. Not a happy thought.
The return is via gravity and 90mm stormwater pipe.
The water was very muddy initially so I made a filter from a mop bucket with many holes in the bottom and about 15-20 layers of quilting batting from spotlight. This has taken most of the mud out over time. It also probably increases the aeration of the water which is a plus.

Each growbed has a gate valve on the input so that I can adjust the flows to even out the fill levels to individual growbeds. This took a fair while to fine tune and would have taken forever if I had used ball valves instead of "John valves". Each valve now has a cable tie to prevent accidental changes to the settings.
As the whole system runs on solar charged batteries it is very important to me that the pump is as efficient as possible.
So the gate valves are set so that the last growbed has a fully open valve and the others are closed just enough to ensure that they all fill at the same time.
The first pump is a big blue unit which is rated to pump about 15000 litres an hour to a head of about 2 metres using about 700 watts of power to do so.
The current pump uses only 250 watts to pump a rated 8-9000 litres an hour and actually only takes about a third longer to pump the same amount of water as the big one. This suggests to me that the big one is actually throttled back by friction in the delivery pipes. This came as a bit of a surprise as I thought short pipe runs and 40mm fittings would not be a real restriction.

Once the water gets to the growbeds it is distributed via a series of 25mm pipes with lots of holes in the bottom surface. This prevents water spray and hence evaporation and also limits algae growth on the top of the gravel. The return water from the beds is restricted by bits of 40mm PVC with just 2x 6mm holes in the lower section. This was just luck and means the return takes about an hour before the pump kicks in again.