General Information

Updated: 04.12.11 By Peter Waddington

General Information – Eric Pond Filter Systems – ALL MODELS.

Once again, Eric Filter Systems are complete stand-alone units; they require no other equipment either before or after them when installed. It is important to note that because of the materials used in the build, these units are heavy, please ensure there is enough manpower available when installing the unit.

The Outer Boxes.
These are hand-welded to shape from black polypropylene sheet 9mm thick. This material is virtually indestructible in normal usages and in all climates unlike some other plastics that become very brittle in cold weather climes. Polypropylene is used widely as a work surface in food preparation premises, laboratories and hospitals where good hygiene is paramount as it is virtually impervious to staining. Eric filter units do not support algae on the inner walls of the units.

The only plastic fittings that can be welded to polypropylene are those also manufactured in polypropylene.

There are only three polypropylene fittings used in all Eric units as follows:-

A 1.5” male threaded barrel nipple is welded centrally in the exit wall. This outlet is to be connected directly to the female threaded inlet of most water pumps available today that can handle the flow-rate requirements of all Eric units. After connection, the delivery outlet of the water pump can be increased to 2” (63mm) bore for return of water to the pond. It is advisable to fit a 2” bore (63mm) ball valve in these lines to control the flow rate required. (Please note – Today, many return lines enter the pond below water level and to avoid back-siphon during discharge of the units a simple brass one-way threaded flap valve can be screwed directly to the male nipple before the pump is installed. These flap valves are not spring-loaded as many others are and so friction-loss is kept to a minimum.)
The central 4” bore inlet socket at the start of the unit is for connection to UPVC pressure tube from the bottom drain of the pond. As mentioned above, UPVC tube cannot be attached to polypropylene by using the normal solvent cements and so this socket is ‘plain’ inside the Eric unit to allow the standpipe to operate and ‘threaded’ underneath the unit to allow a 4” or a 110mm UPVC barrel nipple (supplied) to be screwed into the socket. In this way Eric units can be connected to either 4” bore UPVC tube or 110mm bore UPVC tube, which is the common choice of tube used outside the UK and USA.
There is an identical socket next to the central inlet socket above. This can be fitted to the left or the right of the central socket when the unit is being made. This is the 4” waste socket that also serves as an overflow and should connected and then taken to the main sewer or discharge box/soak away. This socket assembly connection can also be specified in either 4” or 1110mm bore. Even in the smallest Eric Two unit, the internal water pressure when filled is significant hence the two steel support frames on all units are there to ensure that the units are perfectly rectangular when running. The top frame also conceals and protects the UPVC air supply to the filters housed below this frame.

As a result, Eric outer boxes are almost bombproof whether installation is in-ground or above ground. If an in-ground installation is the choice, all that is required is the narrow concrete base. Once in-situ the landscaping can be taken directly to the outer walls of the box, which makes excavation and installation extremely economical.


  • The Contents inside the Box.

    Around 65% of the end cost of Eric units is for the items supplied and fitted within the boxes…

  • Installation Information.

    Installing any Eric Filter unit is painfully simple as they are all flat-bottomed boxes that sit on the top of a flat concrete base. However it is VITAL that the correct water…

The Contents inside the Box.

Around 65% of the end cost of Eric units is for the items supplied and fitted within the boxes.

These are as follows: –

a. Polypropylene ‘O’-ring Standpipe.

This is made from heavy duty thick-wall tube with an internal pull bar at the top for placement and removal when discharge is carried out. The tube is machined near the bottom and a 0.25” rubber ‘O’ ring is fitted to this recess – simple but extremely effective.

b. The Brush Box.

In the Eric Two unit, the Brush Box holds two rows of five filter brushes whilst the Eric Three and Eric Four units have identical Brush Boxes that hold three rows of five filter brushes. It is vital that these boxes fit tightly inside the unit however all brush boxes can be lifted out and turned from side to side or even upside down if required. The Brush Box outer is formed in polypropylene and the 4” diameter brushes are made from double crimped polypropylene strands onto a central stainless steel core.

c. The Transfer Baffle

This is welded into the structure of the unit and separates the mechanical stage from the biological stage but produces no restrictions at all to the water flow. The importance of this can be seen when a discharge of the filter is carried out and water from the biological stages rushes back to the sewer outlet to flush the brush box also.

d. The Aeration System.

In the Eric Two unit there are two membrane air diffusers; the Eric Three unit has three membrane air diffusers and the Eric Four unit has four membrane air diffusers. The air manifold concealed below the top frame of the units is assembled in solvent-weld ‘GF’ UPVC pressure specification tube and fitting and enters the inside of the unit through holes drilled into the frame at the correct points before final finishing of the frame. The rubber membrane diffusers are made specially to cover the entire width of the box and each one can be removed if ever required by way of a screwed union fitting built into the manifold. The entire manifold can be connected directly to the outlet of the air pump with the 1.5m long, 5/8” diameter braided extension hose that fits to the manifold and then directly over the delivery outlet of the air pump before securing with the jubilee clips also supplied. Increasing the outlet of the air pump by not using the inside of air delivery bore thus reduces friction loss further so that we can get the maximum possible performance from the air pump itself.

e. The EricMat Blocks.

These are responsible for much of the remarkable performance of all Eric Filter units. This grey material is 30% denser than the best quality blue/green filter mat and is unique to Eric Filter Systems. This is supplied from the manufacturer (ENKEV) in 500mm x 380mm x 19mm sheets specifically to form the EricMat Blocks. These blocks are built with two polypropylene sides and held together with four stainless steel bars secured by nylon-threaded screws at both ends. In all, seventeen sheets of 19mm thick EricMat are used to make up one block. Size for size one of these blocks produces three times the surface area of a cartridge formed from traditional blue/green filter mat sheets. As with the brush box and despite the necessary tight fit inside the box Ericmat Blocks can be lifted out and re-positioned if required.

f. The Sheet Holder

There are two tracks near the end of all units that hold a single sheet of grey filter mat, which is 38mm thick and 20% denser/firmer than blue/green filter mat – again, this is unique to Eric Filter Systems. I do urge users not to insert this sheet during normal running operation as this is really intended as a mechanical ‘end strainer’ for the rare times when very fine suspended algae may be present in the water. After usage it can be rinsed and stored.

g. The End Baffle

This clever circular plate is centrally fixed 25mm proud of the end wall exactly at the centre of running water level. It works similar to a vertically positioned bottom drain top, which is fed by horizontal-flow water. It is there to keep the moving block of water as large in diameter as is possible before being picked up by the water pump. Several ideas for this baffle came up originally but this one works superbly.

Installation Information.

Installing any Eric Filter unit is painfully simple as they are all flat-bottomed boxes that sit on the top of a flat concrete base. However it is VITAL that the correct water level is achieved in these units in order to get the very best out of them bearing in mind that all Eric Filter units are gravity-fed from a bottom drain.

Before calculating the level at the top of the concrete base that the unit will sit on, the final pond water level should be pegged exactly.

The maximum possible depth of water inside all units is 550mm, after this, any extra water will overflow. The perfect depth of water required in all units WITH NO PUMP RUNNING is 535mm. This dimension, together with the pegged water level of the pond enables the perfect depth of the top of the concrete base to be calculated.

At this static level where the pond and filter are equal, the tops of the Brush Box and EricMat blocks will be submerged. The standpipe will be in the correct position to block off the waste outlet and obviously the inlet line from the bottom drain is open.

When the water pump is switched on at approximately the correct flow rate, the level of water in the unit will begin to drop visibly. At the same time, the water level in the pond will increase but this is hardly detectable because of the larger surface area of the pond. After four minutes or so (depending on flow rate applied) the system will stabilize at normal running level. By this time the depth of water in the unit should be around 500mm and lapping the tops of the Brush Box and the EricMat Blocks.

At this point, the standpipe should be marked at running water level, once this has been marked a 0.5” hole should be drilled through the wall of the standpipe with the bottom of the hole at water level. This now becomes the system overflow where any excess water is automatically removed to waste.

In addition to this, all units have their own drain line purge assembly which can be checked periodically by simply removing the standpipe and allowing water to rush in from the bottom drain and then be taken directly to waste without passing into the filter itself.