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karimwassef
09/18/2015, 11:12 PM
I have an old Kent hi-s RODI 150gpd system without a pressure gauge.

My current setup is ~ 660gal and the summer evaporation is insane.

Every 2 months, my DI is consumed and my TDS increases. I change the filters, but not necessarily my membrane.

Every 4 months, I've been changing my membrane - so three times a year. I'm doing this because I have no way of telling when the membrane is actually used up.

Other than adding an output pressure gauge, is there a way to tell?

DasCamel
09/19/2015, 12:00 AM
Every 4 months seems very high to replace the membrane. The ratio should be 4-6 carbon filters to every membrane change. Any idea how many gallons your using per month?
How about input TDS for the system?

Yes, pick up a pressure gauge. I would also track post membrane TDS, that creeps up when the membrane starts to fail.

thegrun
09/19/2015, 12:20 AM
Test your RO membrane with a TDS meter, not by pressure drop. When your outgoing TDS relative to your incoming TDS starts to rise, it's time to replace your RO Membrane. Even with your large tank your RO membrane should be lasting you a year or more.

karimwassef
09/19/2015, 01:09 AM
That's what I thought too.

I had assumed that the DI getting exhausted so quickly was an indication of the RO allowing a high TDS through, but I can measure it.

Obvious to check, but I just missed it.

I estimate my evaporation rate to be 3-7 gpd.

I have a dehumidifier and an AC (depending on temperature) in the garage to export the water into the garden. The outlets are almost a continuous thin stream - there's freshwater algae growing at the outlet before it goes underground.

bdehlin
09/19/2015, 01:43 AM
The RO membrane should last your at least a year from the sound of it. I'd get an inline tds meter installed add it will probably save you money in the long run.

karimwassef
09/19/2015, 02:19 AM
Maybe it's my DI that's just running out prematurely? If my RO output was good, why wouldn't my DI last longer?

My TDS goes from 0 to 3 unless I change the DI every 2 months...

thegrun
09/19/2015, 08:36 AM
For the amount of water you are making changing DI resin every 2 months does not seem excessive. That said, you should run two DI canisters if you are not already doing do. When you start to see your TDS climb move the #2 DI canister to the #1 position and then replace the resin in the old #1 and move it to the #2 position. This will allow you to get full use of your DI resin. When you only use a single canister, you have to discard the resin before it has been fully exhausted, running two canisters in line allows you to get full use of your resin. The second canister will quickly pay for itself.

DasCamel
09/19/2015, 08:47 AM
You can just order a standalone DI canister right and plumb it in series right?

Mark9
09/19/2015, 09:41 AM
You can just order a standalone DI canister right and plumb it in series right?

Yes. I have a second plumbed in right after the units out.
Further to your membrane, check the tds at the tap, then check before the di. If you rejection rate is not in the low 90's, then you replace the membrane.
(Tds before di / tds at tap ) * 100

http://i1090.photobucket.com/albums/i375/bigmark9/Mobile%20Uploads/2015-09/34343468-191F-41E7-A51D-F41A5072C010_zpsdad9eqis.jpg

karimwassef
09/19/2015, 11:16 AM
Thanks.

I have all the canisters from an older RODI - three more canisters to use.

I travel A LOT so minimizing maintenance and extending the life of cartridges is important.

Any ideas on how to make this into an annual or biannual maintenance activity?

DasCamel
09/19/2015, 11:19 AM
Yes. I have a second plumbed in right after the units out.
Further to your membrane, check the tds at the tap, then check before the di. If you rejection rate is not in the low 90's, then you replace the membrane.
(Tds before di / tds at tap ) * 100

http://i1090.photobucket.com/albums/i375/bigmark9/Mobile%20Uploads/2015-09/34343468-191F-41E7-A51D-F41A5072C010_zpsdad9eqis.jpg

Thanks. I'm kinda lucky, haven't checked my tap but with the BRS 75 membrane, I'm getting 1 TDS before the resin.

Mark9
09/19/2015, 01:46 PM
Thanks. I'm kinda lucky, haven't checked my tap but with the BRS 75 membrane, I'm getting 1 TDS before the resin.

Very cool. I get 57 out of the tap, 3 before di, resin lasts along time.

Buckeye Hydro
09/19/2015, 02:37 PM
A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or more of the prefilters (all the filters that touch the water before it reaches the RO membrane) is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove much of the chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Remember that all the water you process, both waste water and purified water, goes through the carbon block.

Regarding your RO membrane and DI resin, use your total dissolved solids (TDS) meter to measure, record, and track the TDS (expressed in parts per million [ppm]) in three places: 1) tap water, 2) after the RO but before the DI, and 3) after the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 ppm. Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO membrane housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 96% (i.e., they reject 96% of the dissolved solids in the feed water). So the purified water coming from your 100 gpd membrane would be about 16 ppm (a 96% reduction). Filmtec 75 gpd (and below) membranes produce purified water (a.k.a. “permeate”) more slowly, but have a higher rejection rate (96 to 99%). The lifespan of an RO membrane is dependent upon how much water you run through it, and how “dirty” the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the TDS in the water coming into the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce purified water more slowly as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the TDS in the RO water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, your resin needs to be replaced. Sometimes you'll hear people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin high TDS water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.

Additionally, don’t forget to sanitize the entire system at least once per year, and wash and lube your housing o-rings with food-grade silicone grease every filter change.

Russ

Mark9
09/19/2015, 03:32 PM
Where does one get food grade silicone grease?

Buckeye Hydro
09/19/2015, 03:33 PM
I'll PM you a link

karimwassef
09/19/2015, 03:43 PM
When I got my system - back in the last millennium I think - they didn't come with TDS or pressure gauges. Mine came with a box and two little lights - red and green. You push a button and if the red light comes on, you change everything. It was never red - even after running for a year ! :D

So I changed it once a year - but that was an in house reef running 77F and only 200gal.

This tank is 660gal, in the garage (in-wall), and runs at 85F...

I got a pressure gauge and a two reading inline TDS.

SpectraPure
09/21/2015, 10:53 AM
When I got my system - back in the last millennium I think - they didn't come with TDS or pressure gauges. Mine came with a box and two little lights - red and green. You push a button and if the red light comes on, you change everything. It was never red - even after running for a year ! :D

So I changed it once a year - but that was an in house reef running 77F and only 200gal.

This tank is 660gal, in the garage (in-wall), and runs at 85F...

I got a pressure gauge and a two reading inline TDS.

Karim,

Are you on municipal water or well water? Also if you have the rodi system automated on a float it creates TDS creep.

Jeremy

karimwassef
09/21/2015, 12:53 PM
I am on city water. We have a lake reservoir.

I trigger on an ATO to replenish my ATO container that's 100gal.

Once it starts, it runs for at least 15min of fill up.

SpectraPure
09/21/2015, 02:51 PM
What is the pressure and what are the TDS reading? When you take the tds reading do you let it run for 10 minutes?

Jeremy

karimwassef
09/24/2015, 09:24 PM
The inlet pressure is 80psi. The outlet (between RO and DI) is zero?

karimwassef
09/24/2015, 09:36 PM
TDS in is 233
TDS out is 6
So 97% rejection rate at 150gpd with an inlet of 80psi.

karimwassef
09/24/2015, 09:45 PM
I changed my DI resin two weeks ago and it's already changed from green to brown - completely!

I decided to check my TDS post DI and it is 15!

So depleted and leaching in 2 weeks??

I'll let it run for 10mins and check again.

karimwassef
09/24/2015, 10:02 PM
After 10 mins, it's down to 7.

Now I'm confused

mr9iron
09/24/2015, 10:17 PM
Are you leaving the RODI unit on all of the time, and if so is the resivoir controlled by a float switch? If you allow the unit to make small amounts of water it exhausts the DI resign much faster IME. I find its better to make large batches of water instead of several smaller batches.

karimwassef
09/24/2015, 11:53 PM
The RODI isn't on all the time. It usually runs about 5 gallons at a time.

The reservoir is filled based on a float switch.

KStatefan
09/25/2015, 06:11 AM
After 10 mins, it's down to 7.

Now I'm confused

As your systems sits with no flow you will get TDS creep. Which means the first rew gallons will have a higher TDS than after the system runs for a bit.

Buckeye Hydro
09/25/2015, 06:28 AM
On the small residential-scale RODI systems used widely in this hobby, like you have, the TDS will drop pretty quickly after you turn the system on. Here's some example data from two test runs on a system similar to yours that had a 75 gpd membrane:
http://i224.photobucket.com/albums/dd293/BuckeyeFS/Graphs/TDSCreep_zps2523e7a5.png

You'll see that it took about 60 seconds for the TDS to get down to where you'd expect/like it.

Russ

Buckeye Hydro
09/25/2015, 06:33 AM
If you have your system set up such that it makes 5 gallons at a time, and its a 150 gpd system, you should make 5 gallons in about 1 hr 15 mins. But you said "Once it starts, it runs for at least 15min of fill up." So I'm not clear - something seems confused here.

So realize that for the first minute or so every time it kicks on, your DI resin is taking a bit of a hit. If you can set it up such that it kicks on less frequently, and stays on for a longer period of time, that would help.

If it only ever kicks on for 15 mins at a time, then yes, I'd do something to change the set up. Our Hi-Lo Controller for instance was designed to address this exact situation.

Or you can address it manually by putting a micro ball valve in the tube that feeds your 100 gal reservoir. Open the valve and fill the reservoir. A float valve in the reservoir will keep it from overflowing if you forget about it. Then manually close the valve, and only open it weekly or so. When you do, the RO will kick on, and it will stay on for an extended period.

Russ

mr9iron
09/25/2015, 06:42 AM
If you have your system set up such that it makes 5 gallons at a time, and its a 150 gpd system, you should make 5 gallons in about 1 hr 15 mins.

So realize that for the first minute or so every time it kicks on, your DI resin is taking a bit of a hit. If you can set it up such that it kicks on less frequently, and stays on for a longer period of time, that would help.

Russ

This has been my experience thus far as well. If you have the ability to make larger amounts of water than just 5 gallons I would. I went from making 5 gallons to waiting until my Brute is almost empty before making water and have seen my DI resign last much longer now. Give it a shot, and report back.

Buckeye Hydro
09/25/2015, 07:01 AM
This has been my experience thus far as well. If you have the ability to make larger amounts of water than just 5 gallons I would. I went from making 5 gallons to waiting until my Brute is almost empty before making water and have seen my DI resign last much longer now.

Smart!

karimwassef
09/25/2015, 01:08 PM
It runs for a minimum of 15mins but usually more like an hour, hence the 5gal estimate.

I can let it run lower so it only refills once a week. My reservoir is 100gal so it can keep the tank happy for a three weeks without issue.

I let it run for a couple of hours and the post DI was flickering between 0 and 1ppm.

So -

Does it make sense that my pressure is 80psi before the membrane and zero after? (I think yes).
Do I need to change my RO with TDS at 240 in 15 out ? (don't think so)
Do I need to change my resin after two weeks given that it has changed color but my post DI reading is hovering at 0-1? (Don't think so)

SpectraPure
09/25/2015, 01:21 PM
The RODI isn't on all the time. It usually runs about 5 gallons at a time.

The reservoir is filled based on a float switch.

Karim,

The systems should never be automated by float valve. The float valve is for overflow protection only. Having a system on a float valve being automated only makes smaller amounts with super high tds coming out of the membrane and into the DI. This will rapidly kill your DI, and produce what we call TDS creep.

The better method is to make 10-50 gallon batches at once. This will enhance the life of your DI by 3-6 times. Also I am not sure that the green resin is all that great. Not all resin has the same quality or life expectancy.

Jeremy

Buckeye Hydro
09/25/2015, 01:23 PM
Does it make sense that my pressure is 80psi before the membrane and zero after? (I think yes).
Yes - nearly all of the pressure and flow goes out the waste water tube. So when you hear one of us RO geeks talk about the "low pressure side" of a system, now you understand what we're referring to.

Do I need to change my RO with TDS at 240 in 15 out ? (don't think so)
If you do the math, that comes out to a 93.75% rejection rate. Not great, but not horrible. I don't know what membrane you're using, but if you do, compare that 93.75% to the membrane spec. Regardless, you can let it go or get a new one - you should just understand that if you had a really good membrane, your RO water would be about 5 ppm, and your DI would last 3 times as long as it is now.

Do I need to change my resin after two weeks given that it has changed color but my post DI reading is hovering at 0-1? (Don't think so) No. Trust your meter. But keep an eye on it because that 0 or 1 ppm reading may change soon. Treat the color change as a reminder that you need to start paying closer attention to the meter.

Russ

karimwassef
09/25/2015, 02:20 PM
Is resin rated? Is there high capacity resin vs. ???

If I buy a pump, I know the flow and pressure as well as power. But I thought resin is resin?

I buy the Drs Foster's AquaFX DI

If it varies, it should have a rating?

Buckeye Hydro
09/25/2015, 02:25 PM
"Resin" IS NOT "resin." There are many many different types, and quality varies all over the board. Buy your resin from a reputable dealer in the water treatment business.

Russ

karimwassef
09/25/2015, 02:31 PM
I get that. But other than the source of the DI, how do I know?

My TDS in is actually 233 and out is 6. I was thinking of 15 from my DI. But that brings my RO to 97%.

I'll redesign the refill to separate it from the float.

Buckeye Hydro
09/25/2015, 02:34 PM
Yep - 97.5%. Not the absolute best, which might give you ~1% better, but 97.5 is pretty darn good.

Re the resin - you can't/won't know. That's why I'm encouraging you to buy from someone actually in the business, that you trust; rather than from a pet supplies vendor.

But that's up to you!