[jo5hm4n]

So i've had my 450GPD RO System now since August 2016.  Can't believe how fast that's already flown by!

So far i haven't changed any prefilters or any of the membranes.  Everything is from PureFreedom.  They advised when to change, but i want to hear from actual "window cleaners" who i usually find know best

So how often should i be changing the filters/membranes?  A set amount of Water going through/pure produced or do you go off, when the TDS starts to rise or something?

So water before RO from tap is around 165, and after RO comes out at 10 originally, but after around a month or so, it was down to about 5 or 6.  Polished off with DI.  Haven't checked in a few months, but what should i let it rise to before you think it's reasonable to change filters/membranes?  Going through about 1250-1500L Pure per week, only since October.  Before then was using around 1000L per week since about August.

Also do you change everything at the same time, or do you change filters more than membranes?  I'm clueless :O

Membrane Costs
10" 150 GPD Reverse Osmosis Membrane = £37.60 & Vat x 3 membranes = £135.36

PreFilter Costs
10" Reverse Osmosis Pre-filter Set = £13.92 + Vat = £16.70

So based on these costs, i don't mind changing the prefilters often as it's actually quite cheap!  The Membranes not so much though, so advice please guys

[Spruce]

The only time the tds will rise because of prefilters is if the sediment filter becomes blocked and reduces water flow and pressure onto the membranes.

If the prefilters are filthy and the TDS starts to rise, then the possibility is that you have left the filter change too long. The carbon block prefilter has a limited service life and once that's up it allows chlorine through. Chlorine destroys membranes.

The most important filter is the carbon filter.

I don't know what c/b filter you have but the 10" fiberdyne filters have a service life of 38,000 liters which includes waste and pure.
You know how much pure you use and you know the ratio of pure to waste, then you will have an idea when to change your filters.

The easier way is to fit a cheap water meter before the r/o and change filters when the service life is up.

Some on here believe that you can leave the prefilters much long than that. Maybe you can. How do the suppliers know how long the c/b will last with your water supply? They don't, so they will use a 'safe' figure. It might be that the chlorine in your water is only a 1/3rd of the base used used in the calculations. That could mean a c/b filter will last for 114,000 liters.

SeanK on here is a great advocate of leaving the prefilter changes longer. He maintains its pointless spending £300 (hyperbole) on prefilters to make the £135 membranes last another year. What he says makes sense but you have to start somewhere.

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[jo5hm4n]

Okay thanks for your detailed reply.

Ive worked i probably use around 35-50k Total water every 6 months, so i am now thinking i could probably change all prefilters every 6 months at £16.70 a time, it's peanuts really if it means i get more out of the membranes.

Also, i am more concerned how long should membranes last?  Also an average amount of water put through them or?

Is there any way to test how much chlorine is in your water?  Personally i do think my water has alot of chlorine in it, there is always a strong smell for starters if nothing else.

I dont mind changing pre filters twice even three times a year just for peace of mind too be honest,  i am more worried about making sure i don't have to change the membranes too often.

I rarely use any resin any more, so i save enough money that way, used to spend a fortune on resin.

[Spruce]

Some cheap c/b filters only have a service life of 10,000 liters.

How long should membranes last? Easy answer is; how long is a piece of string?

Our tap water is 105ppm today and we haven't a high calcium content in the water. Our kettle 'furs' up but takes a long time. and its just a thin layer. The membranes in my 450GPD lasted 6 years with 2 of us and a 3rd in the last 9 months.
Currently we have a 4040 and the membrane in that is nearly 4 1/2 years old and still performing as it did when new.

I bought the first r/o (450GPD) second hand. It was a year old and had never had prefilters changed until I bought it. Those membranes only lasted 2 years.

If you have a high calcium content or very hard water, then your membrane may last a year, might even get 2 years from them.

The systems Brodex sold always had premature membrane failure as they sold their systems with only a sediment filter and no carbon block.

You can get chlorine testers from any swimming pool outlet or from Ebay. It consists of a test tube that you fill to a line with water. You then drip a chemical supplied into the test tube, shake and then compare the colour of the water against a colour sheet. I think we used to put 3 drops in.

http://www.ebay.co.uk/itm/Easy-To-Use-Swimming-Pool-Test-Kit-Chlorine-Bromine-PH-Tester-Hot-Tub-Testing-/181445331614?hash=item2a3efc0a9e:g:tlIAAOxyLm9TBzPg

It wasn't very accurate but it was enough to give us an idea of how much chlorine we had to add to our swimming pool water each evening in South Africa. In summer we used more chlorine than in winter.  If you notice the colours on the chart are very close to each other and difficult to judge as the tester always seemed to be a colour between.

I now see there are electronic chlorine testers but I have no idea how good they are

http://www.ebay.co.uk/itm/pH-Cl2-Chlorine-Level-Tester-Swimming-Pool-Water-Spa-Meter-Monitor-UK-/231881916985?hash=item35fd3d4239:g:xLUAAOSwd0BVwYQB

The other issue is that its more difficult trying to get a test sample after the prefilters - well it is on my 4040.

When we get advice that the water board will be flushing the pipes I'm inclined to only run my r/o at night to ensure I don't get a higher concentration of chlorine into my prefilters.

We don't get a chlorine smell from the water tbh, even when we draw water first thing in the morning.

The problem we have is the amount of sediment in the water, not the amount of chlorine.

.