Koi

For effective biological filtration to occur, it’s essential that enough solid material is removed from the water before it enters the biological chambers of your filters. It is also important that the level of waste is kept to a minimum because it will limit the effectiveness of your biological filtration and also harbours parasites and bacteria. The alternative to mechanical removal is to use a settlement chamber, usually in the form of a vortex.

What is a vortex?
A vortex is a cylindrical chamber which tapers into a funnel at the bottom. Incoming water spins around the circumference of the circular chamber – the water normally flows to about a third of the way up the unit – just above where it starts to ‘funnel’. Once the water is spinning inside the vortex the flow slows, allowing waste particles to fall out of suspension and collect at the funnel in the bottom of the unit. Waste collects around the central drainage point. The diameter of this drain will depend upon the size of the vortex; a larger unit will require a 2–3in drain whereas a smaller unit will need a 1.5in drain. These waste drains are generally controlled by a slide or ball valve that can simply be opened to allow the waste to discharge. When the water in the vortex leaves the unit via an outlet pipe at the top, it should be relatively waste-free.

Installing a vortex
A vortex is usually used as the first chamber of a filter system and works best in gravity-fed systems – the water flowing into the unit will travel at a relatively slow speed because it should enter the unit via a 4in pipe from the bottom drain. On gravity-fed systems the chambers will need to be installed so that the top of the unit is slightly higher than the water level in your pond (by 1in or so) – if your pond is flush with the ground then the unit will have to be sunk in-ground.
If you want to use a vortex on a pump-fed setup the unit would have to be positioned so that the outlet is higher than the pond, as the water would flow from here into the next chamber which, in turn, would need to have an outlet above water level. The amount of settlement may be reduced as the water will spin faster due to pump pressure. If you decide to install a vortex on a pump-fed system but eventually realise that the amount of settlement is limited, you can always use the chamber for brushes.
• You may need to install multiple vortex chambers if you will be passing more than 2,000–2,200gph via gravity through your system
• If your pond has multiple bottom drains, the best option is to install a vortex and subsequent filtration system on each drain
• When pumping from a vortex to a bead filter, for example, ensure the outlet isn’t too close to the top of the vortex chamber or it will suck in air

What size?
• Go for the largest-diameter unit possible – this will give you the slowest flow of water through the unit and cause maximum waste settlement.
• Opt for a unit which has a large distance in height from the inlet and the outlet. A good distance between these levels will increase settlement by causing the water to spin more before it leaves the chamber.
• If you are limited in space and still wish to install a vortex it is worth considering the size and flow rate of your unit carefully.
• Cons: a correctly sized vortex unit will have a large footprint, especially if your pond is over 4,000 gallons.

Written by Keith Holmes