Lesson learnt from my first pond – filter design

Being my first pond and also due to space constraint, the design of my first pond filter has many shortcomings and areas for improvement. These are the lessons learnt and features which was incorporated into my second pond filter design and third pond filter design.

Separate Drain and Pump Chamber

My first pond’s filter (above) does not have a separate chamber to house my drain pump. I need to stop the pond water return pumps during maintenance and turn on the drain pump to remove water from the filter into the drain. That is not a big issue.

The bigger problem is with this: when I removed the 3 standpipes in my pump chamber to flush the dirt from the bottom of my filter, the waste water and dirt from the bottom of the filter chambers are mixed with the regular water in the pump chamber. I need to flush out all the water in the pump chamber before I can turn on the main pumps again. This makes the process of removing the waste from the bottom drains of the filter not efficient and unless I remove a substantial amount of water, some of the dirt are circulated back to the pond. Filter maintenance and water changes take about one hour.

A better design, which was used in the filter for my second and third pond, is to separate the drain/sludge chamber from the return pump chamber as shown below.

Instead of using standpipes, ball valves are used to open and close the bottom drains. The photo (actually from my current pond filter) below shows a sludge chamber with drain pump and ball valves in operation.

A long PVC pipe, with tailored ends as shown, allows the valves to be operated easily from above.

With this design, I can continue to operate my main return pumps while I extract waste water from the bottoms of the filter chambers. This facilitates easy and efficient partial water changes and clearing of the waste collected at the bottom of the filter chambers. It is so easy that which I can do this almost daily or at least weekly.

Need for mechanical filtration or settlement at the filter inlet

Due to space constrain in my backyard, my filter does not have many chambers. In the case of my first filter, my filter mats act as a mechanical filter in the first chamber. This means that the filter mats gets choked after a few months. The symptom is lowered water level in the pump chambers. When these happens, I will have to remove all the filter mats from the first chamber for cleaning, and thereby disturbing the bacteria essential for biological filtration. Quite a lot of work for me too. Not good. Unfortunately, the filter for my second pond did not provide for a mechanical filtration in the first chamber as well.

My third pond filter did! It has a chamber (photo below) to allow for solid waste to settle before going into the filter media. Visible at the bottom of the settling chamber are the inlet pipes from the pond’s bottom drains. Standpipes can be inserted into this inlets to close them off during filter maintenance.

After the settling chamber, the first stage of the filter provide mechanical filtration by using brushes. This is to trap solid wastes and debris like fallen leaves which can then be removed and hosed down when needed.