[ian1965]

Good morning all. I have been getting through my 4040 membranes rather to quickly.
I can get my tds down too about 3 or 4 but my waste ratio is more like 40 waste 60 pure to achieve . My question is is it better to have a higher tds with a better 60 - 40 waste ratio.

[Spruce]

Good morning all. I have been getting through my 4040 membranes rather to quickly.
I can get my tds down too about 3 or 4 but my waste ratio is more like 40 waste 60 pure to achieve . My question is is it better to have a higher tds with a better 60 - 40 waste ratio.

What membranes are you using?
What is your tap water tds?
What is your tap water pressure?
Where have you measured your pure tds from.

It's generally accepted that you need a waste to pure ratio of around 60 waste to 40 pure.

Our tap water pressure is 55psi atm and I have an HF5 Axeon membrane in my r/o which will be 10 years old next month. It's still producing water at a rejection rate of 97%. Our tap water tds is between 120 and 130ppm and pure out of the membrane (before DI) is 3ppm. I do not have a booster pump.

I have found on my setup that the r/o's sweet spot is a waste to pure ratio  of 55 waste to 45 pure.

[ian1965]

i am using a  Spectrum SRO-4040-2500
My tap water is high at around 320
Not sure of tap pressure but use a booster pump.
I have a tap to convert to measure pure before putting pure into di
Also have water softner salts before booster pump.

[Spruce]

i am using a  Spectrum SRO-4040-2500
My tap water is high at around 320
Not sure of tap pressure but use a booster pump.
I have a tap to convert to measure pure before putting pure into di
Also have water softner salts before booster pump.

I think you need to adjust your flush valve/gate valve to get more waste water as it may help to extend the life of your membrane.

Saying that your rejection rate is 98% which is pretty good.  I doubt you will get anything better than that. I've played around a bit with waste to pure ratios. At 50/50 my pure output increases by 1ppm. If I go to 40/60 the pure tds reading increases considerably.
If I go the other way my tds remains pretty constant until 70/30 when again the tds starts climbing as the water pressure on the membrane drops. At 60/40 I will be using much more water, production is slower, but my use of resin will remain the same.

Softener salts do help the membrane, as they remove calcium and magnesium from your water and replace those minerals with sodium ions. Balancing an r/o waste to pure isn't just a simple turning of a gate valve to increase or decrease waste water. More  is involved. For example, if you are a water meter, adjusting that waste ratio could add more to your water bill than the extra cost of resin and reduced longevity of the membrane.

[AuRavelling79]

Might be controversial but if I were getting 3/4 ppm I would not bother with resin.

[Smudger]

as above I haven't used resin for several years now -higher TDS from tap - and I get 006 and will goto 015 before changing the membrane

Darran

[NWH]

I have an HF5 membrane which has been used outside for 10 years and I still get 2-3ppm from it it’s been frozen literally  and defrosted in warm water,this has happened a few times over the years and I’ve almost given up on it but it’s still kept on working just the same output but in all honesty I think I’ve been lucky.

[Spruce]

Might be controversial but if I were getting 3/4 ppm I would not bother with resin.

It's what works for us as individuals. I know that at 5ppm I can see ever so faint spots on our lounge windows in the early morning sun.

Would a customer notice them? I very much doubt it. But personally, I'm happier working with water at 0ppm. But that's me. It's not really a problem for me, as 6 litres of resin lasts me about a year before the tds creeps up to 1.  In my starter days, Peter Fogwill told me not to bother with resin at 4ppm, but that he wouldn't let it go much higher than that.

What I do know is that our lounge windows are noticeably full of spots when cleaned with 15ppm.

I also believe that the composition of your water in your area makes a difference. If that 5ppm still consists of a lot of calcium, then spotting would be more evident than if you had very little calcium content in your water. But that's just my opinion and not based on any scientific fact.

[NWH]

Yeah I always use 000 any issues I’ve ever had with ali windows have always been with water slightly over 000 although they can spot anyway it’s worse with water over,I don’t know what the problem is anyway if you’re RO is producing 3-4 resin will last ages.

[ian1965]

Thanks for the reply's Sorry one more question if you are using the water softeners do you ever change the beads? 

[NWH]

You’ve got to have seriously hard water to be using a softener my water is on average 250-300 and with 2 pre filters-RO-Resin it costs pennies to run over the year.

[Smudger]

no, I looked into it several times - too expensive and very faffy when making 2000/2500 litres a day

Darran

[NWH]

Ionic love selling bags and bags of salt keep it for slippery paths lol.

[windowswashed]

Changing the carbon filter regularly helps prolong the life of the membrane considerably.

[Spruce]

Thanks for the reply's Sorry one more question if you are using the water softeners do you ever change the beads?

I think you need to phone Doug at Daqua or June at GAPS Water and have a chat with them.

[NWH]

I wouldn’t think June would recommend a softener but if she did I’d take her advise there’s not a lot she doesn’t know about making water.