RO/DI machines ???????

i have a small reef system 2 1/2 years old now but the ammount of water i use to change wouldnt have made it worth my while getting one so all my water has been done by my lfs

now i have a 300 ltr tank to fill up it would be beneficial to get one of these systems and i have found a 4 stage system good for the money and all above board
just a few thing that bug to me and am wondering if anyone could help me on this

this system is capable of sifting through 50us gallons per day
now the filters are recomended changing every four months but would this be on the presumption that i am pumping 50gal every day for four months or would this mean that i could run the equivilent as i am changing nowhere near this at all.
i intend on using a tds meter so could i change all the filters once i see the ppm goin up?

i also take into consideration that different areas have different water conditions, our water in th uk isnt too bad but as usual do contain the bad stuff, luckily not too much in my area.

even so at the moment i would probably be paying £10+ every month on water made up for me and so i guess this would pretty much pay for itself over a short period of time but i wouldnt want to waste money changing filters that probably didnt need changing
on the filters is there a way of telling if one of the filters are full instead of changing all of them?

sorry if im asking a million questions i find it interesting to learn as much as i can but search for the answers and get nowhere

 

Your TDS meter will tell you all you need to know with one exception. Change out your carbon filter as recommended by the manufacturer if your water supply uses Chlorine or Chloramines.

 

thanks good point on that
il check with the seller first if its a sealed cartridge save some monies. good stuff the carbon but its a shame theres no way of knowing if its full followed by it leaching back into the system when it is probably messing it all up

 

TDS meters tell you absolutely nothing about when to change the prefilter and carbon block and the prefilter and carbon block have very little to absolutely nothing to do with final TDS.
The prefilter and carbon are there solely to protect the RO membrane from suspended solids, big particles, and chlorine not TDS or dissolved solids which is the job of the membrane and DI resin. You change the prefiter and carbon every 6 months like clockwork regardless of how mcuh or how little water you have made. It is also possible they need changing sooner than that if you have high sediment or particulates in your wate rthat would plug or foul them causing a pressure drop to the membrane.

A good prefilter and carbon block will be in the 0.5 to 1.0 micron range andeasily last the 6 months if you have normal water conditions including free chlorine or chloramines. Don't buy any filters larger than 1 micron and don't buy the unit if it has a little horizontal DI filter as they are inefficient and cost more to own and operate over time due to more frequent replacements.

 

thanks for the info much appreciated
on the DI part of the system as this is a smaller machine it does have a 650ml DI cartridge this is refillable but i see most systems run a three stage system without this, am i better off looking for a threestage or would i be able to bypass this part as it seems theyre only clip hoses

 

Don't really pay much attenion to the number of stages, its really what is in the stages that counts.
My perfect basic reef quality RO/DI woule be the following:
1. 0.5 micron absolute rated prefilter in a standard 10" vertical canister
2. 0.5 or 0.6 micron Matrikx+1 20,000 gallon carbon block again in a 10" vertical canister
3. A Dow Filmtec 75 GPD or GE Water 100 GPD RO membrane (same thing really, both do 75 GPD at 50 psi)
4. a 10" vertical DI with a refillable cartridge filled with 20 oz of fresh nuclear or semiconductor grade mixed bed Di resin

Along with the above you would want a TDS meter, handhelds like the HM Digital TDS-3 or TDS-4TM are good basic models, an inline pressure gauge to monitor prefilter condition and pressure drop and a capillary tube type flow restrictor. You could also add a DI bypass valve so you can use RO only for things like drinking and cooking.

Thats about as basic as it gets and still have true reef quality water with good filter life and long term cost of ownership.