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Average membrane lifespan GPD450

Den

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What would the average lifespan be of 450gpd membrane

tap pressure is 65psi 

tds approx fluctuates between 290 - 330

was getting average 007 from 300 when new just over two years ago, now I’m getting 014 from tds 310. 

I use approx 500l a day five days a week.

is it time to change my membranes? 

 
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What would the average lifespan be of 450gpd membrane

tap pressure is 65psi 

tds approx fluctuates between 290 - 330

was getting average 007 from 300 when new just over two years ago, now I’m getting 014 from tds 310. 

I use approx 500l a day five days a week.

is it time to change my membranes? 


Your membrane is removing 95.5% of the dissolved solids in your water. At one time I was advised that 94% was the general point when membrane replacement should be considered.

Membrane longevity depends on several different factors, the main being regularity of replacing the carbon block prefilter. It can also be down to your water composition (what the dissolved salts are in your water supply), how often you flush and your pure to waste water ratio.

Some of the cheap carbon block filters have a service life of about 10,000 liters. This includes both the waste and pure. So if your pure to waste ratio is 2 waste to 1 pure then you will use 3 liters of water to produce 1 liter of pure. So using this senario your carbon block filter will be processing 7500 liters a week or 30000 liters a month. If you are using a one of these cheap filters then you should be replacing them 3 times every month.

Once the service life of a carbon block prefilter is complete, the filter will just allow chlorine through it. Chlorine destroys membranes so reduces the life of your membrane.

If you are on a water meter, limiting the water going to waste will save money on your water bills but will also mean a reduction in membrane efficiency and longevity and an increase in resin costs. But it all about economies of scale.

If your water has a high calcium content or is chalky then your membrane won't last as long.

We are very fortunate in our area. Although our water is sometimes laden with sediment, our water composition is very kind to membranes. Mine is 6 years old now and still performs at 98% efficiency. But my Fiberdyne 20" c/b filter gets replaced every 77,000 liters without fail.

.

 
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Yes my prefilter filberdyne get changed every month thank you for all the info, I think I will order some from Doug and change them next week,   as the @Part Timer said they will play on my mind other wise ?

I would hazard a guess and say my waste is approx 60% and we have high amounts of lime scale in our water whether that plays havoc with our membranes I don’t know? 

 
Yes my prefilter filberdyne get changed every month thank you for all the info, I think I will order some from Doug and change them next week,   as the @Part Timer said they will play on my mind other wise ?

I would hazard a guess and say my waste is approx 60% and we have high amounts of lime scale in our water whether that plays havoc with our membranes I don’t know? 


Yes, lime scale wouldn't help as it blocks up the fine pores in the membrane material.

Unfortunately you are one of those who will probably have to replace membranes more often. Is there a lot of water softener use in your part of the world?

I'm not saying that having to replace membranes less often will justify the cost and maintenance of a water softener.

 
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Yes, lime scale wouldn't help as it blocks up the fine pores in the membrane material.

Unfortunately you are one of those who will probably have to replace membranes more often. Is there a lot of water softener use in your part of the world?

I'm not saying that having to replace membranes less often will justify the cost and maintenance of a water softener.
I'm not sure to be honest I don't personally or aware that anyone uses them.

like you say Spruce just another cost,  still better than eating thru the resin. 

Thanks again. 

 
90 something quid for 3 membranes from Doug

Not that much really considering what we earn from them

Even replacing yearly would'nt be an issue for me

 
Fitted the new membranes today axeon  have been flushing for3 hours and still getting a reading of 034 how long for the tds to drop? 

 
Fitted the new membranes today axeon  have been flushing for3 hours and still getting a reading of 034 how long for the tds to drop? 
Something is wrong.

Why are you flushing for 3 hours?

Start producing water and then check the pure output after about 5 minutes.

When producing water, what is your pure to waste ratio?

The other thing to check is that you have connected each housing up correctly. If you have connected up a waste into the pure line then you will always get a high pure tds reading.

 
Connected correctly as I done one membrane at a time and only disconnected the screw end 

ratio is roughly 60% waste to 40% pure.

just lifted for approx 5 mins and the tds is now 026

have noticed the water coming out the waste and pure outlets a little faster than normal is that relevant? 

 
Even adjusting the ratio to 2litres waste to 1litre of pure can only get it to 024

 
@Den. I think you need to try to identify which membrane is at fault now. With the r/o running for 5 minutes or so, take off all the pure pipes from the r/o housings and catch the product water from each individually. Then do a tds test on each. You will then be able to identify which membrane is the problem. To catch a sample of pure from each membrane will take a while.

 
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@Den. I think you need to try to identify which membrane is at fault now. With the r/o running for 5 minutes or so, take off all the pure pipes from the r/o housings and catch the product water from each individually. Then do a tds test on each. You will then be able to identify which membrane is the problem. To catch a sample of pure from each membrane will take a while.
Thanks Spruce, have left it running all night and tds is now 020 will do as you say this afternoon thanks again.

 
@Den. I think you need to try to identify which membrane is at fault now. With the r/o running for 5 minutes or so, take off all the pure pipes from the r/o housings and catch the product water from each individually. Then do a tds test on each. You will then be able to identify which membrane is the problem. To catch a sample of pure from each membrane will take a while.
Tested all three membranes 

1. 020

2. 020

3. 021

all membranes returning roughly the same tds.

all pipework is correct as I only disconnected the inlet to each membrane as I changed them.

would the flow restrictor cause any problems? As the flush valve used to be a bit stiff but not any more?

atm I have it set to approx 3l waste to 1l pure and only getting tds 020

having to use it to produce pure but really would like to get this sorted soon.

 
All membranes are returning similar performances.

The only other thing is water pressure. What is your mains water pressure at the tap?

 
All membranes are returning similar performances.

The only other thing is water pressure. What is your mains water pressure at the tap?
65psi min tap pressure, I have ordered another flow restrictor from collins water products that’s where I bought the RO a couple years back. 

 

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