[Nick_Thompson]

Hi Chaps,

We are placing very expensive pre-filters before our R.O. membranes in an effort to preserve their working life, but is this a false economy?

You could buy a new R.O. membrane every couple of years with the money saved on not use pre-filters.

Has anyone tried running their R.O. without pre-filters to see how long the R.O. membrane with last?

Nick

[mufcglen]

I have the 20” fibredyne prefilter fitted to mine, £30 every 5-6 months or so wouldn’t pay for my axeon hf5 membrane after 3 years if it needed replacing by then.
Can’t see any membrane lasting too long with chlorine or sediment etc going through it pal

[Status Check]

Just buy this set.

Not expensive and protects RO

https://purefreedom.co.uk/product/20-reverse-osmosis-pre-filter-set/

[p1w1]

you will need a carbon filter at least, as the chlorine will destroy your membrane

[Smudger]

I followed Vin's advice - I fill a di vessel with activated carbon and use that only need to change once every 4 months ( we make 1500 to 2000 litres a day pure ) the cost is around £12 for a 5 kg bag


as said you can't run an RO without carbon pre filter


Darran

[Nick_Thompson]

you will need a carbon filter at least, as the chlorine will destroy your membrane

Possibly, but testing the produced water for chlorine, after replacing pre-filters in the past, I have been surprised to find that low levels of chlorine have been detectable in just a few days and then quickly increased in concentration thereafter.

I'm wondering if anyone here has ever conducted their own experimentation, in not using pre-filters, to glean something a little more empirical in regards to membrane longevity as opposed to just guesswork.

I think that you will find that even with regular pre-filter replacement, a reverse osmosis membrane will spend most of it's life immersed in some kind of chlorine concentration.

Nick

[Dry Clean]

Nick I have laughed many times at the spend a pound to save a penny pre filter nonsense on here, some people just cant see the wood for the trees and never will, I use a 10 inch carbon filter that gets changed once a year, my 4040 membrane is 3 years old and my last one was around six before I replaced it, what most people dont know it that many of us will have little to no chlorine left in the  water by the time it reaches our taps, fill a glass from the tap and let it sit for an hour then fill another and smell and taste both, if there is no difference to the taste and smell in both glasses then there will be little if any chlorine in the water, there certainly wont be enough to do any damage.
If there is a difference then being a little more cautious with your pre filters might be a better option but even then make sure you are not spending more than you're saving, this alone would rule out the gimmicky Fibredyne.

[dd]

I found using a fibredene filter actually increased the tds of ro water by about 003. I just use a standard 20 inch carbon filter now. If I leave it much more than 5 months my tds gets higher.

[Smudger]

I think your confusing TDS and chorine

Dry clean may be correct but I can taste chorine on a regular basis in our house tap water

Darran

[Stoots]

I use my R.O membrane without any pre filters

Ran out once and never bothered ordering any more 

Not noticed any difference although im sure there is but like you say when you add the cost of filters its probably negligible

The pump on mine stopped working a while ago as well so i dont even use a booster any more

its the most simple setup, 3 x 150 gpd membranes straight from the tap

[nathankaye]

I think your confusing TDS and chorine

Dry clean may be correct but I can taste chorine on a regular basis in our house tap water

Darran

Same here and glad I use the prefilters.   A year back the water board made some changes in my area and ever since you can taste and smell the chlorine. Up until that point, I couldn't. So it's best not to take that chance and not use a prefilter as things can change

[andyM]

Hi Chaps,

We are placing very expensive pre-filters before our R.O. membranes in an effort to preserve their working life, but is this a false economy?

You could buy a new R.O. membrane every couple of years with the money saved on not use pre-filters.

Has anyone tried running their R.O. without pre-filters to see how long the R.O. membrane with last?

Nick

I do think that's a valid point, considering the vast majority of us (apart from the few drawing from bore holes or wells) are sending drinking tap quality water through our RO's.
I have never tried running without a pre filter.
However I use a pre filter (fibredyne) as the first line of defence, as there is always a slim chance that pipe maintenance/ pipe jetting work might happen in the local area. 
As a side note although water companies monitor chlorine levels, as far as im aware they are not legally accountable if the chlorine goes above the recommended safe level.

[Nick_Thompson]

I think your confusing TDS and chorine

That made me smile, Darran.

No, not confused, I was using a sensitive, handheld, chlorine metre at the time.

Nick

[Spruce]

I know Dry Clean and others have different opinions to those I advocate regarding expensive carbon block filters. That's fine. I understand where he is coming from and what he says makes good logical sense.

Doug Atkinson once referred to a test that was done in a south coast city and the results were trace elements of chlorine in the water some days and none for most other days. In another post he recently referred to was in Scotland where test results also showed the same thing. They will be testing for residual chlorine which isn't the same as the total chlorine the water authority uses to treat the water.

If you are in that situation then that's fine. But he also stated, as does the website of the water authority, that chlorine levels are higher the closer you are to the dosing station. Where is your dosing station? I've asked Northumbrian water where ours is and nobody has given me an answer.

Mostly our water is fine straight from the tap and only occassionally smells of chlorine. It was 'worse' at one time as it was regular. But smell will only tell us that we have excess chlorine in the water. Its by no means an indicator of how much is actually in our water at any given time. I don't have a digital chlorine test meter. I understand that an accurate test meter cost a lot of money. A chemist working in our local chemical industry laughted when I asked him if the £13.99 chlorine test meters sold on Ebay will work for me.

So how do you advise every window cleaner on this forum that they can get away with cheap carbon filters replaced once every blue moon when their water delivery might be totally different?

I have repeated stated that our Fiberdyne 20" filters will remove chlorine from 76,000 liters of water. But the specs given by the manufacturer don't give an indication of what the chlorine levels in the water are that would give this 76,000 liter figure. I can only guess that it would be the maximum amount of chlorine deemed as safe to drink. It could well be that the levels of chlorine in our water (my water) is half that maximum. Theoretically that would mean that I could use double the 76k of water safely. If there was no chlorine in the water for days then I could well get a year out of my carbon block.

But I just don't know. So I would always advise to err on the side of caution and follow the manufacturers guidelines. But that's me.