A Guide to Modern Koi Pond Construction

Drains box

The next item to consider now for the filter system is the drains box. This will be the compartment where all the bottom drains from the filters, vortex chamber, and filter overflow system are led. If you intend to fit a sand filter at a later date then you will require an additional run of waste pipe to the drain box, and it may be easier to install this at the time of construction for use at a later date. As it is usually difficult to add anything extra later then it could be worthwhile installing a spare 2" pipe and blanking it off so that it is available later if required. The other important item is a 4" drain from the base of the drains box, and this is connected directly to the main house drains. It is important to ensure that the pipe has a water trap fitted and meets all the local building regulations. The photographs on this page show four different drain boxes, two of them are still under construction.
It will be noted that each of the 2" pipes that are connected to the bottom drains or to the vortex are fitted with slide valves. It used to be common practice to fit stand pipes usually with rubber ‘O’ rings, but now most koi keepers prefer to use slide valves. Another alternative especially with 2" pipework is to use ball valves. These are more expensive, but have a longer life.
The drains box can be fitted in any position in relation to the filters or the pump chamber.

This photo shows that instead of fitting a 4" pipe connected to the main drains then a submersible pump with float switch has been used. This is left switched on at all times, and as the water rises then the pump will automatically start pumping until the water level drops and the pump switches off.This type of system is necessary when the base of the drains box is lower than the main drains. The discharge from the pump is in this case fully piped in, but it is possible to use a flexible pipe.

In this case the three slide valves from the filter bay drains have been led into one common manifold, and this has been taken to the drains box.

The pipe end of this manifold is actually visible in the drains box in the photo below, and is marked A.

TIP. Many people do recommend that you use ball valves for the drains as they are much more reliable. They are quite a bit more expensive than the standard gate valves, but certainly a good investment as they are in regular use.

The three pipes in this case come from the same type of filter system as the photo above, but as there is not sufficient room to easily get up the side of the filter to the valves a separate pipe has been run from each filter drain and the slide valves are fitted close to the drain box.

Both systems are fully acceptable and shows what needs to be done to fit in with the particular situation you are faced with. The only practical difference is that in this case more pipe is used and so the cost will be higher.

This is a drain's box being built into the floor of a filter housing. A pump with a float switch will be added later.
It is important that the compartment is made big enough to cope with the rush of water when the valve is opened. It is better to make it larger than smaller as it cannot be too large.
Check on Page 1a to see the construction of this type of drain box.

Tip. It is a good idea to get the iron grating before you start building the chamber as then you can make it the right size.

On the next page we will look at Pumps & Systems.

Page No. [1] [1a]