A drain box is where the bottom drains from the filters, vortex chamber, and filter overflow system are led. If you want to install any additional features to the pond, like a sand filter then it is recommended that you run spare 2″ pipe and blanking it off so that it is available later if required.
You will also need a 4 inch drain from the base of the drains box that is connected directly to the main house drains. Make sure that there are water traps on the pipe and that the set up meets local building regulations.
Fit slide valves over the stand pipes instead of rubber ‘O’ rings as they are more durable.
Constructing a drains box
Prepare the hole for your filter housing base
Dig a hole for the drain box within this filter housing base
Pour concrete into the bottom of the drain box hole to form the base of drains box.
Build a wall with 18 x 9 x 4 inch concrete blocks, arranging the blocks so that the height is level with the filter room concrete base.
Complete the filter housing base. Lay reinforcing bars, spacers, pour concrete and level as such.
Then start building the walls of your filter system. Render them as required or apply fiberglass if you so choose to do so.
You can add a steel grid over the opening of the drain box so that you can walk over it as well as check the pump and water level.