[simbag]

Thanks again to you all, my knowledge is growing and growing!

Andrew, thanks for your tips for a DIY approach, I appreciate the money that can be saved by going this direction, but I am not confident in being able to build my own system and deal with possible problems. The obvious advantage of a manufactured system is the after sales service.

I could, and most probably will follow steve k's approach regarding the RO unit, and setup a static at a later date.

I started out with a van based RO system with a vessel of water softening resin as the first filter.
Once you have water softening resin in place you do not need to replace it.
It goes before ALL other filters in the same type of cylinder as DI resin...it becomes the first filter.
Its job is to remove calcium and magnesium particles from hard water.
If it is left to the RO to remove these elements, the RO will become clogged and unusable much quicker.
The water softening resin is flushed clean of the magnesium and calcium about every 400 litres of water made.
This is done by flushing a salt water solution through the resin container for about 15 minutes with the solution going to waste.
It is designed to prolong the life of a RO membrane in a hard water area.

Steve can you tell me what RO unit you use, as different manufacturers (and users) have different opinions on the addition of a softener.

Simon

[steve k]

a 40" one. Of course, you do not need a water softener before the RO but where is the calcium and magnesium going to end up?? ...clogging the pores of the RO membrane shortening it`s working longevity considerably.
If you remove these elements from the water passing through the RO membrane, it will last  MUCH longer.  Put a resin cylinder full of softening resin before the RO and that is it. Every couple of days, flush a solution of salt water through the cylinder to a drain.
Once you get to know how the system works, you will realise its simplicity and you will also realise the mark up on a manufactured system.
Every part of a manufactured system can be purchased individually and extremely cheaply. Putting it together is embarrassingly easy and any questions about problems can be addressed by several well informed members of this forum.
Then again, I thought it was rocket science when I bought mine...so I know where you are coming from