r/o unit

[Andrew_x]

anyone have a coralife r/o unit? they're currently on sale at drs. foster and smith.

http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+4395+4418+12093&pcatid=12093

would it be best to go with a 3 or 4 stage?

i was going to get the 24 gpd 3 stage, but now the 50 gpd 4 stage is the same price as the original price on the 24gpd.

any thoughts?


thanks,
andrew

 

[Irene0100]

I have a similar one, 3 stages, which I have had for several years now.
I prefer the design of mine as it has a flush system fitted (just turn a tap on for a minute or two) so dont have to mess about changing pipes like this one suggests.
Also mine is fitted with taps on inlet and outlet pipes so can be shut down easily.
I dont have it running 25 x 7, just a few hours each day when needed. saves a lot of water.

 

[Andrew_x]

what brand is yours irene?

 

[Irene0100]

Hi,
no idea of make, it has no badge on it.
it is fairly standard and takes the normal carbon and filter refils can buy in lots of places.
in pic you can see the back flush tap in Blue,
which I use everyso often (maybe once a month) for a minute or two which reverses flow back through the Ro membrane to flush molecules out.
it has a similar tap on both the outlet pipes so they can be tuned off when unit not in use. if turned off for more than a couple of days I throw the firts 5 mins of water away in case having been standing any bacteria has built up.

 

[macvsog23]

Most R O units are of very similar construction and will perform the same.
The key points to understand are water pressure and water treatment prior to filtering.

The first issue water pressure will directly affect you water flow rate and to a degree your rejected water rate.

Sadly the water suppliers in the UK are now no longer obliged to meet all of the standards regarding pressure that were enforce before the evil capitalists demon Thatcher removed them from the peoples ownership. (OK it’s a bloody joke before I get the bad boy Bob treatment)
You can safely assume that water pressure in the UK will not drop below 1.5 bar. This will at best give a 25 gpd membrane a flow rate for treated water at under 10 gpd. Also this will force a far greater rejection rate and more DS (dissolved solids) will flow over the membranes outer skin; I believe that with out regular flushing this will cause harm to the membrane.

The next issue is the contents of the water before you pass it across the membrane.

Contaminants that are not harmful to humans or that are added to benefit humans can and will kill or damage other organisms.

The most dangerous addition to our tap water in my opinion is chloramines or chloride dioxin.

Both will rot plastic at a rate almost as fast as a acid.

These are commonly additions to a water supply to conform to what is called L8 a way of controlling bacteria in water.
They will not be removed by the carbon block filter in a stranded carbon pre filter and to remove them you would need to fit what are called “cto” carbon blocks

I personally believe that fitting a good quality carbon block filter is the most important step you can take when using a R O unit.

 

[Irene0100]

thats interesting, I have no idea what sort of carbon I am using!
I will have to read the small print when I order next!

 

[Andrew_x]

well, being a plumber, i managed to get a deal on a 5 stage unit made here in the states. not sure the exact manufacturer but will get it tomorrow.

i'll have to look into the cto carbon blocks; are they readily available or do they need to be special ordered?


thanks for the info guys,

andrew

 

[Irene0100]

good. yes mine is carbon block so got the right thing.
hope you manage to fit it ok -well should be a doddle for a plumber -lol

 

[Andrew_x]

got it all hooked up yesterday. marlo, inc 100 gpd 5 stage system. it's a beauty and was a breeze to install. couple trips to the hardware store and an hour or so was all it took.

tap vs ro water params are as follows:

pH - 8.8+ vs. 6.6
ammonia - .50 ppm vs. .25 ppm
nitrite - 0 ppm vs. 0 ppm
nitrate - about the same on both, between 0 and 5 ppm
kh - 5 vs. 1
gh 8 vs. 1

ordered a tds meter through my lfs and should have it in a week or so.

is a backflush necessary? or is it just a reassurance that you're cleaning the membrane a bit more? would backflushing not contaminate the "pure" side of the r/o membrane since you're reversing the water flow and therefore putting "dirty" water through the outlet side of the system?

another thing, is something like kent's r/o right all that needs to be added to the water before it goes into the tank,. or do i still need to add something else (i.e. dechlorinator, etc.) for assurance?

thanks for everyone's help in advance, and now i'm looking forward to setting up my newest addition, a 4 ft, 55 gal tank that will be a planted amazon biotope. only problem is finding somewhere to put it!



andrew

 

[Irene0100]

Hi,
sounds good
I either use kent Ro right with some buffer like waterlife 6.5 buffer, or tropic marin which has buffer included.

 

[Andrew_x]

is the buffer necessary even though the ph is right where i need it? or do the buffers build the kh? i thought the idea of using r/o was so you wouldn't have to adjust the ph? this is confusing!

thanks for all your help irene,

andrew

 

[Lornek8]

is the buffer necessary even though the ph is right where i need it? or do the buffers build the kh? i thought the idea of using r/o was so you wouldn't have to adjust the ph? this is confusing!

thanks for all your help irene,

andrew

Buffers of some sort are required whether they are commercial buffers or simply from the addition of tap water.

RO water is basically pure water, simply H20 (nearly at least). So, any addition of chemicals/compunds/minerals, whether intentional introduced or not, will make a big difference in the composition of the water. This makes RO water very unstable & unsuitable for use without some form of buffering. The idea of RO is to start with basically a clean slate thus making it easier to achieve the desired water chemistry by adding what you need rather than trying to get there from whatever tap water you're stuck with and worrying about whats in the tap water.

 

[Andrew_x]

ok, makes sense since there's nothing in the water to keep the ph from swinging. thanks for clearing that up lornek8.

i've done water change so far with ro right and proper ph 6.5; all fish seem well and happy. will check params later.

thanks once again for everyone's help; it's greatly appreciated.


andrew

 

[Andrew_x]

well the r/o has been up and running for a while now, and i recently checked the ph. it's now pushing out water with a ph of 8.8 to 8.9, instead of the original 6.6 it was making. why is this? i know the unit is working, as the feedwater has a tds of 343 and 2 ml/l of chlorine. r/o water has tds of 25 and no chlorine, with a gh of zero and kh of at or below 1.

anyone have any ideas why a 3 week old ro unit is producing water with such a high ph?


thanks for any pointers,
andrew

 

[Lornek8]

Possibly what little minerals are making it through (TDS 25) is buffering up the pH. Should be a simple matter to buffer it to where you need it though.

 

[Andrew_x]

okay that's what i thought, just making sure no one else had the same problem and knew of something else that caused it. thanks once again lorn.


andrew