SUPADIVERTA - syphonic rainwater diverter

GARDENS

INLINE FILTERS

Varying manufacturers inline filters are similar in performance but AQUATREK recommends the HOLMAN product for the following reasons:-

• The internal filter cartridge is made from a tough but flexible white plastic that clearly shows any trapped sediment. Many other filters are black and have proven difficult to judge where cleaning is best concentrated.
• Aquatrek uses a specialised cleansing instrument for internally cleaning filters, a vintage tried and tested toothbrush which performs better with flexible filters.
• The HOLMAN filter is available in three end sizes, 13mm, 19mm and 25mm. Both ends are removable and size interchangeable, allowing the filter to join different size hoses. The convenience and advantage of clever design is obvious.

Most filter cartridges have mesh aperture sizes ranging from 80mm to 175mm. Manufacturers unfortunately rarely indicate the filter mesh size. A choice and indication of size would be an advantage to consumers.

While suitable for use with mains water, INLINE FILTERS ARE NOT SUITABLE FOR USE WITH RAINWATER HARVESTING SYSTEMS as the internal filter cartridge presents a physical barrier which reduces velocity and the more contaminants it traps, the more restricted it becomes.

LOW COST DIY FILTER

Aquatrek has designed a small horizontal inline sediment extraction system that does not require a filter by opting for Vortex Induced Sediment Separation methodology.
Only a few principles are involved:

• Water flowing through pipe travels faster through the core and slower on the outside extremity due to friction loss and the resultant separation zones or streamlines is known as laminar flow.
• Most sediment will travel along the bottom bed load at a rate slower than the flow of water.
• An internal raised bottom projection, for example a kink in the hose, causes the flow to speed up to pass over and around the obstacle. This results in an eddy (vortex) circulating on the lee side and becoming a bed load trap by holding low inertia particles in eddy suspension and is why underwater obstacles, large rocks for example, cause downstream deposits of thick mud where an eddy has circulated.

THE INVENTIVE PATHWAY

The consistency of enclosed laminar flow makes design modelling relatively easy. By moulding small ledges to the bottom of Perspex tubes and then making a bottom Tee branch (cavity) behind each ledge, we made several simple Tee fittings with varying small internal obstructions for comparison flow testing.
During testing, harvested rainwater was circulated through Perspex tubing at varying velocities and small particles were observed flowing over the barriers and then flow downward into the Tee branch (closed capture chamber) under the influence of the vortex. Varying the obstruction's profile and height made huge differences to the location of the vortex and our team was surprised by the amount of captured fine sediment that was not visible until it had settled in the Perspex branch. Later tests demonstrated that this ultra fine sediment would pass through inline filter cartridges.

AQUATREK WILL NOT MANUFACTURE THIS FILTER!

However, we have found a manufactured flow obstructed 25mm Tee with a 15mm female threaded branch that can be used to quickly make a small ad hoc version. The Tee, plus a 19mm x 15mm male threaded elbow which form the capture chamber, is available online. Polypipe fitted with an inline tap or flushing cap needs connecting to the elbow to seal the chamber and allow draining. Using other Tee fittings with smooth flow paths are of little value to this application.
This DIY cheap as chips curio must only be used horizontally with the branch facing down, works surprisingly well with SUPADIVERTA and is worth fitting. Use 25mm polypipe and 25mm x 19mm reducing joiners to connect to 19mm polypipe. To stabilise bed flow and for best results, a minimum 1.5 metre length of 25mm poly pipe should be used prior to the obstructed Tee fitting.
The concept is easily upsized and testing through Perspex at varying flow rates will show the sediment clumping at different locales. This then determines the best location for the collection chamber at the different flow rates.