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Reverse osmosis owners

I finally broke down and ordered an R/O machine for making water so I no longer have to lug home 10+ jugs a week. I ordered a Captive Purity 3 stage 75GPD unit from Marine Depot. Hopefully it will arrive tomorrow or Wed. as I paid for next day delivery.

I ordered the Flush valve kit which is said to extend the life of the TFC membrane, how long do the TFC membranes usually last? A year or more? Do the carbon block prefilters need to be changed more often than the TFC? I suppose all this will be covered in the manuals that come with it, I'm just excited I guess!

Finally I can drink water from the tap!
Hi Josh,

the membrane usually will last a year or two at the most, it really depends on how high the PH is. Usually water is near neutral unless you have a well with limestone in it!

The carbon prefilters should be changed every 6 months or so, mine is due for a membrane and sump filter change, have to order a membrane soon. The manual should cover everything you need to know about your system.

Good luck and you'll really appreciate the system, they truly are a nessessity when you have a large collection.
The TFC membrane should last 2-3 years. Your prefilters will need to be replaced more often. Every 3-6 months. Depending on the quality of the source water. If your using tapwater with added chlorines it is important to replace the carbon block frequently to keep the chlorines from reaching the membrane and shortening its life significantly. Again it will depend on how much water you use. It should say in the manual how much water you can send through it before it should be replaced. Once you get it set up you will need to get a rough idea how much water you send through the system to produce a gallon of RO water. That will give you a basis to figure out how much water your processing if you use say 10gallons a week. The other thing I would highly recommend is a good TDS meter to periodically monitor your RO water quality.

Here is my last tap water test (using Hagen aquarium water test kits):
Ph. 7.2 - 7.4
GH: 3
KH: 18 (it is salt softened so there is lots of sodium)

I never used the above tap water on any of my plants cos I know it's bad (and I've killed plants before by thinking good water wasn't important).

Hmm, so you're saying the "75 GPD" might be the total water processing per day (including waste water) and it won't actually be producing 75 GPD of pure useable R/O water? That stinks as I was thinking that buying a larger system would mean I could quickly fill up a few jugs quickly each day as I need them.

I just put the TDS meter off for the time being cos I tried to stay under $200 for the startup order. Does the TDS meter simply get dipped into the output water or does it attach to the RO unit itself somehow?
The rating is usually the amount of RO water it will produce in a day.  Not the total amount of water you can send through the system.  This however is very variable since they are tested at a certain temperature and water pressure usually not found in a home.  The colder the source water the less RO water it will produce and the lower the pressure the less it will produce.  It will also probably say somewhere in the manual 75gpd at x pressure y temperature.  It is unlikely you will be able to produce 75gpd.

Some units have flow restricters on the waste water outlet that lets you force more water through the membrane.  Although restricting too much flow out the waste valve may force impurities through the membrane so there is a limit to how much you can do here.

Water softeners are a good to use in conjunction with an RO filter because the sodium ions are blocked easier than calcium ions. This will give you more RO water to waste water. HOWEVER you need to pay much more attention to the quality of the RO water. IF something should happen to the membrane you may inadvertently water with softened water.

Not sure what the TDS meter you can add to your system is.  I would opt for a hand held unit.  You can measure all sorts of things, the RO water, waste water, souce water, water with fertilizer to gage fertilizer level etc.
I'm not really looking for 75 gpd, I don't need that much everyday but I was just thinking this would allow me to quickly (within a few minutes) get a few gallons for watering and the humidifiers anytime I need it.

After I get water from it will it need to sit overnight or anything to let the chlorine dissipate? Since it's city water it's originally got all the goodies. The catalog mentions removing 98% of everything but who knows what it will really do, it's probably not that pure in reality.

Do the hand held TDS meters have a probe that gets dipped in the water or how do you use yours?
Hi Josh, I as well have city water and have had no trouble with chlorine, just change the sumps every 6 months is what I do.
TDS meters usually have 1 or 2 metal contacts/probes that you simply submerge in the water and they record the TDS of the water for you.
I would get a couple 5 gallon plastic containers and just fill them up. Or if you have space a 32 gallon plastic trash can works nicely to store water. Making a very rough guess that your total production will be more around 50 gallons/day because of temperature and water pressure. That is roughly 30 minutes to make a gallon of water. The water is good to go once it comes out of the filter system. You are correct that a good TFC membrane will remove about 98% of impurities. In actuallity it is better at removing some things than others so if you were to do a complete water test it would not show a straight 98% reduction in all dissolved solids. In any event it will be plenty good to use with your CPs

Hanna instruments makes some very nice compact and accurate portable meters.

This is one of their less fancy units that will work well. It is important to get a small bottle of calibration fluid to keep the unit calibrated. Dist1 is the unit you would want. It is not waterproof and requires manual calibration (very easy to do). They do make units that are water proof and some that have automatic calibration but I don't think the extra cost would be necessary for your needs.Hanna TDS meter

Hi swords,

In answer to your chlorine question, no it won't have to sit out overnight to disapate the chlorine.  The carbon filters remove the chlorine so it won't get to the TFM (Thin Film Membrane) membranes, which are made of a synthetic material. A TFM membrane requires the chlorine be removed prior to the water entering the membrane. A TFM membrane has a rejection percentage between 95-98%, which is much higher than the CTA membrane. A TFM membrane will last between 2-5 years.

The above information and more can be found at Watts Premier FAQ

Keep in mind that the filter longevity information is particular to the system sold by this company, but it will give you an idea of what to expect.

Also, I am assuming that you will have a storage tank for "on demand" purified water.  If so, keep a little purified water on hand as it will take a while to charge your storage tank the first time.
  • #10
Dont forget that if your storing large amounts of water on concrete it will eventually become too cold to be using directly on your plants, I usually use a couple of submersible aquarium heaters coupled with a powerhead.

  • #11
The  R/O machine arrived today and of course the sink fitting they sent with it is too large, just to start my day off right!  

The catalogue said it would be supplied with a 3/4" faucet adapter but it's actually a 1" as for a garden hose or something. Nothing in my condo takes a hose that big. The "manual" for this brand is one whole sheet of 8 1/2" x 11" xeroxed both sides...!

So, where can I buy a step down adapter? Does it have to be a special step down adapter made specifically for R/O or will any do? I was thinking of just getting a step down part from the aquarium shop for the Python water changers and attaching the R/O to that to switch between R/O water and regular tap water for dish washing etc. (as the R/O will be hooked up to the kitchen sink).

I thought of "hardwiring" the R/O under my sink but I don't have metal piping, only the flexible hose type stuff. I used that cos I don't have the equiptment to work with copper pipe when I replaced my faucet last summer. The "manual" that came with it doesn't even mention that this can be set up that way anyway.

Anyway, how do you folks have your R/Os hooked up? I won't be able to hook anything up til my next days off (Thurs, Fri & Sat) but I'll be reading and looking for good ideas on how you guys do it, thanks again for any ideas!
  • #12
Hi Josh, my system gets adapted to the water via a self piercing valve tap that is connected to the main cold water faucet line. Then a green feed line connects to the outlet and powers the system.
  • #13
The plumbing sections at hardeware stores (Like Home Depot) have addapters for changing the size of the connectors. I know this since I had to do change the fittings of a filter to connect to the garden hose. you just screw one the adapter to the other fitting and that's it.

  • #14
Cool, thanks Joel,
I didn't wanna have to order one for someplace special and wait another week or two! Are all thread paterns the same on faucets? The thread holding the aerator on my faucet seems awful shallow but then again the old faucets aerator was corroded on and I hadn't seen the threads in some time.

BTW nice signature!