Ro Reverse Osmosis Filter Maintenance

[steelhealr]

We all have our particular areas of interest in nano reefing. Reverse osmosis filters are not one of mine. Nothing easily came up on a search with regards to maintenance, so, I hope that members who are strong and particularly knowledgable in this area will help build this thread. I'll start it off with some basics and I hope others will fill in and correct. I hope we can avoid 'installation instructions' and focus on function, maintenance and just plain old figuring out when your filter is reaching it's life span. Thanks in advance. SH

Basic Intro

There is a commonly quoted saying here on this forum that, as nano reefers, we are not really aquarium keepers but water managers. One of the key ingredients to a successful nano tank is providing clean sea water that is as pure as possible. Using RO water fits the bill. Water out of the tap may contain many unwanted ions and minerals, some of which we don't test for but over time may contaminate our tanks. Some of these include:

1) phosphates
2) nitrates
3) copper
4) heavy metals, among many others

So, for many, if within your budget, an RO filter is the almost perfect addition to that long list we make prior to putting the aquarium setup together. So, after the tank is filled and we've been using the filter, how do we keep ourselves out of the dirty water doghouse, ie, how can we tell that the RO filter needs either replacement or new parts? Hopefully, we'll all kick in and help out with this.

Terms

GPH - gallons per hour
PSI - pounds per square inch
TDS - total dissolved solids

RO/DI Filter Anatomy

1) red intake tubing
2) yellow waste water tubing
3) blue outflow tubing

A) Prefilters
B ) RO membrane/filter
C ) De-ionization resin/filter
D) Crushed coconut shell carbon filter

a) flow restrictor and membrane flush valve (in normal operating position in pic)
b ) auto shutoff valve

Filter Flow

1) Tap water enters via the red tubing
2) water flows thru the 3 pre-filters and
3) passes thru the auto shutoff valve and into the RO membrane
4) water exits the RO membrane and goes via the yellow flush tubing and goes to
5) the deionization filter
6) the water then exits the DI resin/filter to enter the final coconut shell carbon filter
7) RO/DI water exits here

Testing your Filter

Brine Ratio

Not my area of expertise, but it's the ratio of good water to bad water.

1) fill 8ozs of water from the blue tubing exiting the RO membrane after throwing the first 4-5 ounces away
2) At the same time, measure the discharge water from the yellow tubing (open the black valve, parallel to the tubing....pink small case a)
3) When the 8 oz of water is collected from the RO membrane, measure the volume from the discharge tubing.

Yellow discharge tubing volume / RO membrane volume = brine ratio.

Recovery Rate

A little confusing. During the above test, measure the time it takes for the 8 oz glass to fill. The result will be ozs/sec. Convert to gallons/hour.

3600 secs in an hour
16 cups in a gallon

3600/ secs to fill 1 cup = cups per hour/16 = gallons per hour which is the rejection rate

TDS

Measure the TDS with a TDS meter at positions:
-tap water
-after the three pre-filters (pink 3)
-after the RO membrane (pink 4)
-after the DI filter (pink 6)
-after the Aqua faucet (blue tubing 3/pink 7)
- after the flow restrictor/discharge (yellow tubing 2)

PSI Data

The RO filter works on water pressure. There are three critical water pressure readings to obtain:

1) The red tube feedline (1)...pressure readin should be at least 45 PSI

2) The white tubing after the 3 prefilters (pink 3)..this should also be at least 45 PSI. If it is 5 PSI lower, than recommendations are to replace them

3) The blue tube from the RO membrane (pink 4)...should be at least 2/3rds the PSI of the previous pressure. If not, flush the RO membrane by opening the flow restrictor valve (pink small case a) and flush it for 15-30 minutes

HIGH TDS and LOW PSI may mean you need to have an electrical booster pump.

Replacement Recommendations

Points of wearout:
1) RO membrane
2) auto shutoff valve
3) tank if you have one
4) flow restrictor and yellow discharge tubing gets caked
5) 'O' rings get old and crack

Change filters every 6 months if your use is 150 gallons/month

System is probably near dead at 5 years and may require total replacement.

Comment

I hope that all the RO experts will make any corrections, add useful simple tips and also feel free to comment on how to use and interpret the data obtained, eg, the TDS readings. Thanks for everyone's input. SH

 

[crazyelece]

Some good ways to measure when you need to replace RO membrane is to test the source water and output water with an inline tds meter. You can find them on ebay and they splice right into the system. You need to test before any DI because DI alone can get you a 0 tds reading. It will just need replacing faster if that's all you use. The RO is used to filter out most of the "stuuf" and then the DI finishes to make it ultra pure. A typical tds reading after an RO is <15ppm. If it starts to raise from this the membrane needs to be replaced. You can also use a GH KH test kit. The water should test 0 for both.

 

[drsquirrel]

I know this is an old thread, but since it is referenced(/stickied)... wouldn't it be better to say (@crazyelece) that it's best to test after the RO Membrane and after the DI unit, rather than the source water which doesn't help you much other than a one off test "just to know".

This way you can test the life of both your RO Membrane and DI resin (if you have one of course).

 

[seffieuk]

You have to remember when this was written, 1995 - less people used a TDS meter or for that matter an RO unit!

We now know that testing the source water first before it goes through lets us see how much our lovely RO and DI filters are taking out you would probably do this once at the start, but then you would test the end product periodically so that you know when to change the resin, membranes etc.

Seffie x

ps it is one of the pinned threads that need updating

 

[drsquirrel]

You have to remember when this was written, 1995 - less people used a TDS meter or for that matter an RO unit!

We now know that testing the source water first before it goes through lets us see how much our lovely RO and DI filters are taking out you would probably do this once at the start, but then you would test the end product periodically so that you know when to change the resin, membranes etc.

Seffie x

ps it is one of the pinned threads that need updating

Sorry, I only read the 2005 posting time - though like you say - maybe that's indication that it needs updating

 

[seffieuk]

Sorry, I only read the 2005 posting time - though like you say - maybe that's indication that it needs updating

Never be sorry, its good to pull these things out now and again, dust them off and see how they can be improved fancy giving it a go?

Seffie x

 

[drsquirrel]

This article is good enough as it is really, few changes and some additions (lowering waste via multiple membranes, maybe).

Maybe I could have a try though, something interesting to work on rather than stupid "NAS implementation procedures" and the like

 

[seffieuk]

"NAS implementation procedures"

If only I knew what that meant I would probably agree - but yeah, how about giving it a go

Seffie x

 

[drsquirrel]

Did you actually mean 1995 or 2005? As 1995 the internet was hardly the internet (I do remember the state of the internet then, im not that young).

So who wrote the above? (SH?)

And what would you want out of a new guide? Above it states "I hope we can avoid 'installation instructions' and focus on function" - same as well for a new one? I am a firm believer of understanding how something works makes it better to use, though not everyone thinks like this. Understanding how to install it (maybe not literally... "how to attach it to your pipe" install) is a good step in understanding what goes on

I will have a quick try in the next few days. I tend to write stuff like this for my company (though tech related, which is why I mentioned NAS) which gets boring as it isn't really what my job is and I'd rather do that instead of trying to explain how what I am doing works to others (but something different would be nice to do).