Saturday, May 18, 2013

Greywater System (Update 2)

With reference to my first greywater system which I built a year ago, I can post my review and any changes I made to make the system more efficient.

Well, the first system worked but did not work as well as I hoped for. The problem was mainly the amount of time needed for the system to filter the 100 litre storage tank. Before building the system, I had tested and concluded that a 100 litre would be filtered in a couple of hours. The parallelism of 3 streams which I included should have achieved good results however to my disappointment, it was taking far too long to filter and therefore I was wasting water down the drain.

To speed up the filtration process and not rely solely on gravity I installed a pump. The pump will take water from the buffer tank and pressurise it into the sand filters. At least that was my intention until I installed it and switched it on. After 30 seconds, I identified 5-8 leaks and suddenly one of the sand filters exploded, specifically one of the bottom screwable taps came off together with all the sand! Not much to do. It was obvious that the system coundn't handle any pressure. The drain pipes which I originally used were not the heavy-duty type and I never imagined that a tap would just explode outwards. At this stage I had two options:

1)      Fix the exploded filter (strengthen also the other two) and maybe use PVC glue to fasten the taps once and for all. The problem will be that the sand inside will not be replaceable anymore, something which I didn’t want!

2)      Replace the filters.

I opted for the second option. Although option 1 would have probably worked, I did not want to spend time experimenting with this solution hoping that finally I have no leaks/explosions


 System Overhaul

The changes were mainly at the filtration stage. Both tanks and all plumbing were OK. I scrapped the sand filters and installed four 10 inch standard water filter housing.

The first filter I’ve installed is just after the storage tank, before feeding the pump. It’s a 25 micron wound filter cartridge and its main purpose is to stop particles entering the pump.

The other three filters I’ve installed just after the pump i.e. will be benefitting from the increased pressure. The filters are also the 10 inch cartridges. The filters are;

1)      15 micron active carbon

2)      5 micron

3)     1 micron   

The pump is automatically activated using a float switch installed in the tank and therefore is only active if the tank is full.



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