Challenging yet noble, we aim to tackle the Malaysian health ministry’s statistic.
Even the most simple and economical water filter system’s design should abide by the reference guideline used by water treatment professional worldwide. Failing which, the apparently clean treated water may turn out more toxic than raw water.
Insisting to do it right, we did our best to comply with the tacit rule of water treatment. Hence, the following features are very different from the rest.
(including installation)
Why is backwash after midnight so important?
Simply because the flowrate and pressure is much higher, as compared to daytime, to thoroughly lift up and expel trapped sediments.
Cheap and easily available PVC pipe are made for water to flow through the internal wall. However, when installed in the filter tank, water also comes in contact with the external wall and allows the sand media to rub against the external wall of PVC pipe during backwash.
Normal PVC contains lead (poisonous heavy metal). The sand abrasion may wear out the lead-containing particles of the PVC wall. The escaped lead are eventually carried by the flow of water into your drinking tap. Thus, easiest way to avoid such poisoning is by replacing PVC pipe with the non-toxic ABS pipe.
Cleaning off the printed data with solvent and filling the sharp edge of the pipe are simple alterations we make to perfect the tubes.
The following engineering factors are widely recognised by water treatment professional worldwide, in sizing the tank coupled with specific sand media:-
Service flow (gpm/sq ft) : 3-5
Backwash flow (gpm/sq ft) : 15-20
From the above figures, the required flow for backwashing is obviously much higher (around 4 times) than that of the service flow. The reason behind such strong flow during backwashing is to ensure sufficient lifting force to efficiently dislodge the trapped sediments against gravity. However, during service run, slower flow ensures better filtered water quality.
There is no difficulty for large-scale water filter systems to have a separate pump and a larger pipe specifically for backwash operation. Unfortunately, a similar set-up will be too troublesome and costly for home use. From many years of experience gained in household water filtration. Crosslink found that the required flow for service run at 3-5 gpm/sq ft can be altered upward if finer particle-size of sand is used, instead of the standard 0.6-1.2mm. With the increased rate of service run, we can bring the gap of service flow and backwash flow closer — therefore, eliminating the need for 2 different pumps to cater to the respective flow. Nevertheless, Malaysian city water is usually quite clean. With our domestic filters operating as a secondary filtration, we are able to take advantage Of Our filtered city water by performing frequent backwash — without the worry of fine sand congestion by large unfiltered dirt brought in by the municipal water. By doing so the tank size can also be reduced to match the required backwash flow.
No professionally designed sand filter would have a top strainer installed as it restricts effective draining of sediments during the backwash process.
Not just clean water, but more critically, clean filter
