Pumps and Filters for your Garden Pond - Final filter rebuild

Filter basics      First Rebuild      Second Rebuild


Then one day, I was proudly showing a new neighbour my ponds as he was thinking of building one and was looking for ideas when I happened to say that in the ideal world, I'd move the filters down to the other end of the garden but to do that I would have to move my sheds and completely rebuild the top of my garden again. Even as I said it, I felt light bulbs going off in my head and I knew that I would be having a busy Christmas holiday again that year.

When the time came to move the filters to the other end of my garden, I made the mistake of trying to move the whole system intact rather than dismantling it first. As always, this was being done in the middle of the winter and in this particular one it was very cold. Unfortunately, the sort of plastic that my filter boxes were made from doesn't perform too well when it gets very cold and as a result of trying to save a small amount of time, I managed to crack both my filter boxes. Needless to say, I was not exactly a happy person but life must go on so I had no option other than to get a new filter. I decided to do away with the vortex box because it hadn't been as successful as I had hoped.

The vortex filter is normally used with a bottom drain and the water moves into the vortex relatively slowly and any debris remains intact and is collected in the vortex prior to the water moving into the filter proper. In my case, because I was using a pump in the pond, any debris was finely chopped up as it passed through the pump and therefore much of it wasn't heavy enough to fall out of the vortex. So although the vortex worked as it was supposed to, it couldn't do the job of removing all of the solid matter before it reached the filter. So that's why I didn't think I needed to build another one.

Having decided on the location for my new filter, I realised that it would have to be a free-standing one so would need to be quite robust. The sort of water tank that is used in lofts is quite suitable and I spent about half an hour on the Internet and found this one. Its 1600mm x 500mm x 600mm. So it will hold 500kg of water and therefore, needs a solid foundation. As you can see, I used a double layer of building blocks to do that and also to raise it up a little to make cleaning a bit easier.

I decided that I wanted an additional set of sponges for this filter so I needed an extra chamber to get the water flow correct. Looking at the picture on the right, the water feeds into the right hand compartment and flows down throught course sponges onto the brushes. It then comes back up the narrow chamber before flowing into the third chamber where there are 3 layers of finer sponge over the bioligical media. The water then flows back up into the final chamber which is full of more biological media before it flows out through the 3 pipes at the top of that chamber. The pipes drop just over 1m before taking the water back to the pond where they feed the water in below water level.

As on my earlier filters, I have used copper pipe and plastic waste pipe to control the separation of the perspex dividers within the filter. When the apparatus is out of the filter as in this picture, it is all floppy but once it is fitted into the filter and therefore constrained as to where it can move, it bocomes a fairly rigid structure. Having tried many different ways to seal the perspex to the sides of the filter to get the water flowing in the right direction, I have decided against it. As a good friend of mine pointed out, instead of fighting the water pressure, why not use it to my advantage. So I used small strips of perspex to attach a 100mm piece of liner to the edge of the perspex using the plastic nuts and bolts for fitting car number plates.

The idea is that the water flowing into a chamber can be used to press the liner flap into the junction between the perspex and the side or bottom of the filter and effectively seals off the junction thereby forcing the water to move where we want it to go. The first time that you fill the filter, you might need to assist the liner into place but after that it will sort itself out. There will be a little amount of water escaping around the seal but as you can se from the far right picture, the majority of it will go where we want it to go, the filter will work properly.

These pictures show the brushes and biological media in the filter. And then with the sponges in place. The plastic pipes across the middle section are there to prevent the sponges from floating up to the top of the chamber. The sponges in the middle chamber have the greatest effect on the clarity of the water in my pond and I can actually get away with just rinsing those rather than cleaning the whole filter as long as the water remains clear.

The final pictures on this page show the filter in operation and how I have hidden the filter from view. "Management" is extremely tolerent of all that I do with my ponds, though she cannot understand the need to keep changing things. However, after all the bother with the old brick boxes, I was under no illusion that this time, the end result had to look tidy. So, as the filter is clearly visible from the patio where these pictures were taken, I had to build a cover; its held in place by two hooks and is easily removabale whenever I have to get into the filter for maintenance.

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