[m.b.s.]

dose anyone know if there is a way to purefi the wast water in sted of wasting it i wast about 14 liters an hour but i have only a 100gpd unit as i am starting small and building up to be big time cheers

[m.b.s.]

must be some one out there who no,s

[JM123]

the waste water is exactly that - waste.  The problem is that the waste water from an ro is very very high in tds, so putting it through another membrane will in turn damage the second membrane and you will be left with much more concentrated waste water again!!

What is your tap tds as if it is low enough you could well get away with using 2 or 3 di vessels inline, provided your tap tds is low enough this can work out as cheap as running an ro unit.

[JM123]

oh and I wouldn't worry about wasting 14ltrs a day, its next to nothing.

[Clive McDonald]

Put in search. The more times you run it through the higher the tds.

There is probably a min start point tds before you reach the point of diminishing returns, but i have no idea what that is. Measure going in and going out.

Do you have a pump to put it in the second time? take measurements.

Repeat.

Repeat.

Come back and tell us how you get on. That is why no has answered.

[m.b.s.]

my tap tds is 250  but producing 14 liters an hour not day dont understand you answer rainwater as i am new to this could any one tel me what a 4040 ithink it is called and how much and were from

[KarlJones]

m.b.s,
can you give us a few details, 

How much pure water are you producing?  we know it is 14 ltr an hour of waste but how much good stuff?

What is the TDS of the waste?
What is the TDS of the good stuff?

[Highrise]

I wouldn't like to think how much water I am wasting... I fill up 800Ltrs everyday , Good job I'm not on a water mertre

[groundhog]

We all will be soon

[john tomkins]

the waste water is exactly that - waste.  The problem is that the waste water from an ro is very very high in tds, so putting it through another membrane will in turn damage the second membrane and you will be left with much more concentrated waste water again!!

While your statement is logical, its exact opposite of what the RO-Man upgrade diagram shows. It feeds the waste from membrane 1 into membrane 2 and then into membrane 3 then out to drain.
http://www.ro-man.com/shop/product_info.php/cPath/34/products_id/132
I'm lost

[*foxman]

Merlin 2......................

[JM123]

john - the ro-man systems work in this way to minimise pressure loss, if you were to connect all 3 in parallel you lose pressure, so they have the membranes linked in series, to do this the check valve in membrane 1 opens at a low pressure to allow tap water to move into membrane 2, its check valve then open to feed into membrane 3.  It works but isn't ideal. 

The industry leaders are AquaFX, have a look at the top system in particular and look at how they have fed the water into each membrane at the top via the blue piping.  Its parallel, although there is no booster pump in the pic they do recommend it for pressures less than 80psi.  I used to have one of these systems, water quality was exceptional (001ppm from inlet of 350ppm), it didn't produce a lot of water (about 350ltrs a day) but it ran non-stop for over 2 years except when the filters were being changed.

[KarlJones]

OK, when the check valve is open, then the water flowing into membrane two must be dirtier than the water that is coming out of the mains.  The check valve, as I understand it, is just there to create some back pressure on the membrane and that is its function. 

The way I thought it worked was...
Mains water goes into membrane number one.
check valve is shut to allow pressure to build.
pressure builds, the waste water and clean water are seperated.
check valve opens as pressure builds and allows the waste to flow to membrane 2.

by doing this if the membrane is capable of say 100 GPD, then 100 GPD will be produced through it but lets say it also produces 500 GPD waste. 
Now if you take the 500 GPD waste and also put that through a membrane you get another 100 GPD produced and 400 GPD waste
Now if you took that 400 GPD waste and pushed it through a third membrane you get another 100 GPD pure and 300 GPD waste.
Giving you a total of 300 GPD pure vs 300 GPD waste.

The problem, as I see it, with doing it this way is your pumping higher TDS through the third membrane.
some more hypothetical figures...
If the first membrane splits 300 TDS produces 5 TDS then the remaining 295 TDS would be pushed into 5x300 TDS, the volume of water, ((5x300)+295)/5) so you get waste of 359 TDS going into membrane 2.
again it gets split, the 359 TDS produces 10 TDS and the remaining 349 TDS gets pushed into 4x359, the volume (the remaining waste) ,((4x359)+349)/4) so you get waste of 446 TDS hitting membrane 3.
for the third time it gets split, 446 TDS producing 15 TDS and the remaining 431 TDS is flushed away with the 3x446 water ((3x446)+431)/3).
Giving you two end products.
300 GPD of 10 TDS (5 TDS, 10 TDS and 15 TDS mixed) and...
300 GPD of 589 TDS waste.

589 waste would eat through the membranes too fast so it really is waste.

But if my senario is correct and typical, then is it also true that the third membrane is less likely to last as long as the other membranes, and therefore, should it get changed first.

Sorry if it went on a bit, but it is me and I wanted you to be able to pick away at my thinking piece by piece to show me where i am going wrong.

[Clive McDonald]

There you are mbs what could be hard or clearer than that ?

[m.b.s.]

thanks rain water will be back soon

[m.b.s.]

karljones my wast ise the same as my tap water around 250 but my pure is 0 as it goes through a di after the membrain but if it did not go through the di it would be about 10 cheers

[KarlJones]

m.b.s.
at the moment this seems to be what is happening with your system.
TDS of tap = about 250
TDS of waste = about 250
TDS of RO water = about 10

Now that means that the RO is removing 96% of the totally dissolved solids in your system, so we need to investigate where that 96% of waste product is going, because if it isn't going out your waste pipe, it has to be going somewhere.  An RO does not convert, it filters the water and produces lower TDS than the tap, and higher TDS than the tap, this being waste.

You are currently running "waste" at about 90 GPD (USA).  Your actual system can produce 100 GPD (USA) of good water.  It is my understanding that a single 100 GPD membrane can not reach figures close to 50/50, and 75/25 or 80/20 would be a closer guess. 

What this basically means is that currently, if my figures are right, you would only get about 5 liters if that of RO filtered water an hour out of your system.

You are producing 14 liters an hour of waste, when infact you should actually be producing a lot more waste but a lot more filtered water too.  This is what the TDS readings you have given me tell me...

TAP = 250
WASTE = 250
RO = 10
WASTE = 14 liters an hour
PURE = (unknown but I am guessing 4 or 5)

Your target should be...
TAP = 250
WASTE = 311
RO = 3
WASTE = 45 liters an hour.
PURE = 15 liters an hour.

Obviously hitting every figure in that target is near impossible.

My gut feeling is this, your water pressure is too low, what is happening is that the membrane in your system is having to work too hard to filter the water under this low pressure. You are seeing a very nice drop in TDS but the waste is not coming out of the RO and it is staying inside it, in the actual membrane.   

So the two things, the low waste production and the fact you have totally dissolved solids disappearing lead me to believe that the water pressure is too low, if it is not sorted then your membranes will foul quicker than usual and your pure:waste ratio will be poor.

Solution,  tell someone on here your location, ask them if they can borrow you a water pressure meter and get it checked.  If not I would suggest buying one as your going to want to sort it out.   In the future you can add more membranes to your 100 GPD system and improve the pure:waste ratio even further and at the same time improve production.

Just to put what I have said in some sort of context, I am pretty new (very new) to the science of RO and so you should really wait to see what the others say.  But I can see no harm in getting your water pressure checked and trying to figure out why your waste TDS is not coming out.

hope my babble helped.

[m.b.s.]

thanks for that my presure to the membrain is 50 psi i thought about a ro booster pump but the connection which i hav to the ro system is a atandard hose pipe barb fitting out of my ro system and not a thin pipe to connect to the mains tap only a standerd hose pipe connector

[KarlJones]

Then this is where the other guys come in because when it comes to actual PSI readings and connections my inexperience shines through but when you have the pressure sorted, I would buy that RO MAN 100 GPD upgrade kit after contacting them first to make sure it suits your system.

[m.b.s.]

cheers