[[GQC] Tim]

Just thinking of what the cost of wfp would be regards to changing prefilters.

The recommended life span is 3000 Gallon for a carbon block filter, but almost everywhere, including RO manuals, it says change them every 4-6 months. Now if I do the math, providing you use 300l a day, you need about 600l to make 300l of pure water, with about 300l waste under optimal conditions, correct?

3000 Gallons, is 11356 liters of water. Divide that by 2 to get pure water, then by 300, is 19 days or so.

20 working days a month, so that means about 1 month before you change the filters. Now that is in sharp contrast to the 4-6 months that are recommended everywhere, including on these forums.

Why? Is my math off or, or is it not UK gallons but US? But still that wouldn't be that much of a difference would it?

What am I doing wrong here?

[[GQC] Tim]

No one?

[Old_Master]

3000 gallons is a guide, 4 to 6 months is a guide.
It depends what the TDS and contaminants of the incoming water quality is like.
It is just not possible to give a firm time as in the UK the water can vary from 50 TDS to 500 TDS depending where you are situated even then the TDS of 50 could be made up of more hazardous contaminants than a TDS of 500.

When you consider that filters you are fitting are not just made for the UK window cleaning market, but every country in the World for different pure water needs.
Everywhere uses  the same filters,then you realise that its impossible to give a exact time or flow rate.

Example:- A filter life that is  good for cleaning windows certainly wouldnt be good enouth for kidney dialyises treatment, or the production of medicines.

[[GQC] Tim]

I see what you mean, thing is I bought this flowmaster, and it calculates filter life via the gallons. So that might vary then I guess.

Any idea how many gallons 250tds will get me? Because otherwise that flowmaster thingy will be a bit useless then. 

[brightnclean]

Errr I hate to tell u but it's pretty useless other than to tell u how much water passes thru it 

Change ur prefilters every 3 to 4 months in a hard water area and u will be fine. Ur stressing too much.

[[GQC] Tim]

Wouldn't call it stressing, just can't be bothered to put a date on my calendar for when I need to change them, simple beep will do nicely.

Well, I guess it will be just 3000x4 then lol. 

[ps outthere]

It appears I might have got it wrong as, all the info I have seen suggests you use your TDS meter to determine when to change filters. Have I got it wrong?

[Andrews_Water]

Hi,

The prefilters are there to protect the RO membranes, particularly from chlorine, which will damage them.  If you don't change them, the RO membranes won't last as long, and the TDS from the RO will rise dramatically when the damage occurs, and by then it's too late.  TDS is NO indication as to when to change prefilters.

Yours, Andrew

[[GQC] Tim]

Apparantly if the pressure gauge (after the prefilter) indicates a drop in pressure, then they should be changed. But waterpressure can vary anyway, so I don't think that's such a good measure anyway.

[ps outthere]

Thanks for the info. Will change prefilters.