Designing a pond

How to get the design and planning stage right first time.

Building ponds

Where, how and what materials and equipment. The hard work bit.

Koi Pond Pumps

How to choose and where to buy your koi pond pump.

Koi Pond Filters

Selecting the correct filter for your koi pond.

Koi Pond Food

Choosing the right food to keep your koi fit and healthy.

Koi Pond Plumbing

Pond plumbing may sound complicated to the un-initiated, you may think of plumbing a Koi pond in the same way as plumbing a house. However, it is a much simpler job with much fewer complexities.  There are two basic types of pond plumbing systems – one for gravity filter installations and one for pump fed.

Pumped filters. 

In pump fed installations the pump is sited in the pond, connected to the filter inlet with flexible hose. A UV unit is often installed between pump and the filter.

You should fit a slide or ball valve immediately before the filter inlet so that the filter can be isolated for maintenance. Pipe work between the pump and the filter is under pressure and so should be at least 1.5” to avoid unnecessary loss of flow. 

Try to situate the filter as near to the pump as possible with as few bends as possible in order to maximise flow rates. Failure to do this can reduce the rated pump output and put pressure on the pump leading to premature failures. 

The filter itself is situated above the water level of the pond so that water is returned to the pond by gravity. On the return side of the filter, use at least 2” pipe work to return water to the pond.  This will maximise the return flow, which is not under pressure from the pump. If you can, use 3 inch pipe, or if the filter allows, twin 2 inch pipes can be used, but do remember, a single 3” pipe has a larger bore area than 2 x 2” pipes and a single 4” pipe has a larger bore area than a two 3” pipes. Whatever you choose, it must be sufficient to carry the filtered water back to the pond at the same rate as it is being supplied by the pump. Failure to do this will result in a filter overflow.

For types of pumps available, see our koi pond pump page.

For types of filters available, see our koi pond filter page.

Gravity filters. 

With gravity filter installations, the water level is the same level in the filter as that of the pond, with the filter residing in a nearby chamber, excavated at the same level as the pond. 

The filter input is fed by pressure of gravity, which forces water through a 4” pipe buried in the ground under the pond to the filter.

The 4” pipe runs from a bottom drain in the lowest part of the pond and runs horizontally underground and into the filter. #It is advisable to fit a slide or ball valve immediately before the filter to separate pond from filter for maintenance. 

After filtration, water is pumped from the filter mounted below water level and connected to a UV if fitted. Suitable 1.5 inch pipe work then takes water back to the pond, usually via returns fitted into the pond walls. If pipe runs are very long, you should consider using 2” pipes to avoid flow losses. Again avoid any sharp bends in return pipe work. You will have to fit a slide or ball valve immediately after the filter, and before the pump in order to accomodate maintenance of equipment.

If you can, fit at least two pond returns in opposite corners of the pond, in orxdder to promote a circular flow of water. This will mean that solid wastes are swept towards the lowest centre point of the pond and back towrdas the bottom drain again.

Do bear in mind though that more than one return will require balancing valves. This is because water will always take the path of least resistance and so follow the shortest or straightest return pipe. The valves will have to be set so that each return flow carries an equal amount of water.


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