Nothing to do with sales people mate, My reasons are more for how much faster i produce water by changing them and the fact that i have destroyed my membranes by not (i think that was the reason they shot so quickly but i dont know 100%)
I change them 2-3montly, so 7 sets cost around £60-70 ish...
7 sets x 3 months = 21 months...its a bit cheaper than £100 (not much granted) every 12 months, and i know that i produce water quicker when there reasonably fresh...
I'm not arguing with you mate, do what works for you...i was just talking from experiance
I agree with what you have stated.
The 10" Fiberdyne prefilter Gardiner sells will treat 37800 litres of water (figures provided by the manufacturer.) If you have a restrictor that gives a 3:1 waste to pure ratio then each 1 litre of pure will need 4 litres to process. This means that this filter will give you 9500 litres of pure. (For the 3 of us this filter will last us 2 weeks.) If you are using an ordinary CAG filter then these have a service life of 2500 American Gallons or about 9450 liters (figures provided by the manufacturer.). These will be good enough to process 2300 litres of pure.
If you are using 300 liters a day then the Fiberdyne needs to be replaced every 31 working days (approx 6 weeks) and the CAG filters every 7 working days (approx every 10 days).
We use 20" prefilters with clear bowls on our 4040 so we can see at a glance what state the sediment filter is in. The Fiberdyne 20" filter is good for approximately 77k liters of chlorine removal. We have our waste to pure ratio at around 50/50 so expect about 38k of pure from that. This means we need to change the chlorine filter every 6 weeks.
These figures show you how important it is to replace your prefilters regularly.
The first r/o we bought (3 x 75GPD RoMan type filter) was second hand and needed replacement membranes at just over a year old as the previous owner didn't regularly replace his prefilters. I think the first time they were changed was when he sold the unit to me. Anyway I replaced them with 3 x 150GPD membranes and changed prefilters every 3 months. (It was just me on my own in those early days.) Those 150GPD membranes lasted over 6 years and supplied enough water for 2 of us for 4 years of that time.
I'm a great believer in replacing filters regularly as the cost of membranes and resin quickly add up. Running the system to manufacturer's guidelines means that you can always know and trust that the water in your tank is 100% without having to continually check that it is.
Spruce every figure you mention is nothing more than speculation as you will see on the filter packet it all depends on the amount of sediment or chlorine in the water.
As you have no way of measuring this then like I say your just speculating.
Just stop and think about what a sediment filter does, its stops sediment getting to the R.O. so the only way it will damage a
R.O. is if it breaks down and allows the sediments to get to the R.O.
Again this wont happen because the carbon block will still stop the sediment even if the paper one falls apart.
So its not important to change a sediment filter at regular intervals.
As for the carbon filter do you honestly believe that something so cheap would be anywhere near as accurate as it states on the packet ?
For gods sake they are mass produced for a couple of pence in China.
Please explain to me why my R.O. is still going strong after 6 years when Iv never changed a pre filter more than twice a year
since I installed it. According to your figures it should have been wiped out years ago.
Most R.O. membranes fail early because they are not used properly not because of pre filters.
R.O. shock would more than likely be the main suspect.
I take your comments on board.
Firstly, the reason why we change our sediment filters that regularly is that they get blocked and starts to restrict water flow. After a month ours come out full of red sludge and slime. We can see the pressure drop before and after the prefilters as I have gauges on each side of them.
So I guess that I should have stated that the sediment filter will stop the carbon block filter getting blocked up with sediment.
In the early days we used CAG filters which were changed every 3 months. They weren't sediment filter as well. Any sediment in the water would find their way through to the r/o membrane.
Over the years I have noted that some use more water a month than we do and still change their prefilters every 3 months with standard carbon block prefilters and haven't had adverse effects with r/o deterioration. Window Washers on this forum was one of them. According to the label on these CAG filters our filters on the previous r/o would have reached their service life along time before we changed them with no apparent deterioration of the membrane. So your argument has some validity.
However, Vin from Perfect Windows in Southampton has has no end of trouble with his 4040 membranes. GAPS water identified that chlorine as the problem and he fitted a large DI vessel filled with granulated carbon as his carbon block prefilter. That was over 2 years ago and he hasn't reported an issue since.
We have no way of being able to measure accurately how much chlorine is in our tap water. The swimming pool chlorine testers are hit and miss even at best. All you can do is follow the manufacturers instructions. If you extend the limits of those instructions, then you take the risk. If it works for you, which it obviously has done, then great. But that doesn't mean that the identical procedure will work in another location in another part of the UK for someone else.
So when you advise someone, you have to follow the guidelines the manufacturer laid out. If you advise someone that you only need to change your prefilters once a year and he experiences membrane failure because of that, your advise was incorrect and he has suffered financially because of it.
IMHO we have to be so careful when giving out advise and what works for us may not be correct for the next person.