RODI water and TDS

[fixedpoint]

I'm battling an algae outbreak in my tank. In the quest to find possible nutrient sources, I bought the HM Digital COM-100 TDS meter to double check my water. The filter system uses a three stage process + chloramine filter + deionizer. I replace the DI resin about every 3 months but I haven't changed the other filter cartridges in about a year (total system water 50 gallons with weekly 20% water changes and top off). After filtering, I store fresh water and mixed salt water in 32 gallon brute containers.

Here are the results of my tests:

source water: 390 ppm TDS
output water: 2.2 ppm TDS
fresh water container with 1 week old water: 10 ppm TDS

I plan to test again after changing the filters tomorrow

Questions:

1. Clearly 0 ppm TDS is optimal, but what is acceptable?
2. How does a closed lid brute container in a garage containing RODI water increase the TDS of the held water? Is there anything that I can do to prevent it?
3. How long is it okay to store water before use?
4. Do you periodically clean your containers? If so how?

[Ron Reefman]

Questions:

1. Clearly 0 ppm TDS is optimal, but what is acceptable?
I have a big RO system and when I don't run DI it has a 10 to 15 TDS and I use it. Most of the time I run DI and it's zero. I have a friend who uses well water from the tap and dechlorinates it. The TDS is over 100 and his 220g tank does OK. It's really a matter of what makes up the TDS. If you have a TDS of 50 and it's all stuff like salts, it's OK (not great, but OK). On the other hand if you have a TDS of 2 and it's copper, you have real issues. So most people push for the lowest TDS they can get because who knows what is in the water?

2. How does a closed lid brute container in a garage containing RODI water increase the TDS of the held water? Is there anything that I can do to prevent it?
Because the brute container was already dirty when you put the water in. If the brute is fairly new it may have oils or other contaminants that should be cleaned off. I'd do a bleach wash and a vinegar wash and an RO/DI rinse. Then try some RO/DI water in it and see what you get.

3. How long is it okay to store water before use?
If you keep it moving and aerated (a good pump that is enough flow to make the water surface 'boil', and don't over heat it (hot garage and hot pump) it should keep for weeks anyway. I keep RO/DI water in a plastic tank for weeks at a time and my TDS may go up 1 or 2 points if at all.

4. Do you periodically clean your containers? If so how?
Once a year I wipe out the inside of my storage tank with a lint free rag and rinse it with RO water. I wash out my brute trash can mixing station the same way after every time I make new salt water.

[shifty51008]

Rodi water is so pure that it will attract any dirt and dust floating in the air, that is where the higher tds is comming from.

Keep in mind you wanna change the filters every 6 months regardless of how much water you make as you could start growing bacteria in the filters

[CStrickland]

It would be good to check the tds before the di stage too. Your unit should have a flush procedure like a valve or just removing the di. I keep that ro under 10 tds, and the di is just polishing off the last bits. The water should be pretty clean coming into the di or you'll burn through them faster than necessary. Each stage does diff things and needs to be working properly.

[thegrun]

I have a slightly different take:
1. Zero is the only acceptable TDS reading IMHO unless you spend a lot of money to get a detailed annalisis done on the water you have no idea what is in the TDS reading over zero, it could be completely benign, or it could be something very bad for your tank that will concentrate over time.
2. Assuming this is a food grade Brute trash can, it's possible that either the can was dirty when you filled it either from dust or the oils used in manufacturing. I like to clean new (and old periodically) Brute trash cans first with a 5:1 RO/DI and bleach mixture, then vinegar, then a good RO/DI rinse.
3. In a sealed container you can store RO/DI water indefinitely, no need for heat or water circulation.
4. See #3 above.

[fixedpoint]

Thanks for the feedback. I cleaned the filter canisters and replaced the media and resin. The output from the RO stages reads 18 ppm TDS and the output from the DI stage is 0.2 ppm TDS. After my current batches of RODI and saltwater are used, I will clean those canisters thoroughly as well. I'll post the results of sitting water at that point.

[shifty51008]

what is your tap water TDS and pressure? 18 after RO is alot. my tap is 530ppm and only 4ppm after ro

[fixedpoint]

Tap water is 390 ppm. The pressure was 55-60 psi. Also, I was concerned that perhaps the new filters may have some release of carbon or other material so I flushed the system for awhile before taking measurements.

Over the past year, I don't ever remember seeing readings on the RO output TDS meter lower than 10 ppm and more usually in 15-25 ppm range. Also, the 18 ppm reading was checked on both the RO output TDS meter as well as the HM-Digital TDS meter.

[PeterHall]

I let my tds get up around 8 before changing the DI resin. Had a bout with cyano. I ran a lot more media and got some rock from someone breaking down their tank. I felt like the rock had some excellent bacteria on it because most of my algae is gone. I would say maybe it's time to change your sediment, carbon and DI resin but also run some phosphate media

[ericarenee]

Originally Posted by thegrun

I have a slightly different take:
1. Zero is the only acceptable TDS reading IMHO unless you spend a lot of money to get a detailed annalisis done on the water you have no idea what is in the TDS reading over zero, it could be completely benign, or it could be something very bad for your tank that will concentrate over time.
2. Assuming this is a food grade Brute trash can, it's possible that either the can was dirty when you filled it either from dust or the oils used in manufacturing. I like to clean new (and old periodically) Brute trash cans first with a 5:1 RO/DI and bleach mixture, then vinegar, then a good RO/DI rinse.
3. In a sealed container you can store RO/DI water indefinitely, no need for heat or water circulation.
4. See #3 above.

1+
This is what i do...
every 12 months i will let my 55 gallon tanks go down to about 10 gallons each and start the pump to circulate thru all 3 of them. Hook a flex house to the inlet inside each container one at a time. And pout 1/2 gallon of Vinegar into the Containers.. Using the hose spray out the sides of the Containers... This cleans the Containers Pumps and Plumbing...

Drain and rinse the tanks with another 20 gallons of Fresh RO/DI Water. then let them air dry . Refill and continue to use.. Can not GET INSIDE The tanks to scrub them with a brush as the top opening is too small..

I never let tds above 2....

[CStrickland]

Your pressure is low, but idk if it's low enough to need a pressure booster. The water must be pushed through the filters, too slow and it kinda goes around them. Another way to check filters is the waste ratio, it should be 4:1. So like I have a gallon jug and a 5g bucket with a line drawn @ 4g. When the jug is full the bucket water should hit the mark. It seems like less waste water would be good, but unless you mod for it it usually means the filter is inefficient.
Also, the new filters have to be good quality and well-packaged, old dried out generic ones can mess you up.

This stuff is good for saving you money on filters and getting the most out of your rodi, but I don't think it's going to make a big diff in your algae. Idk about the holding bins cause I make water weekly for a 10% change and topoffs on my 50g. So I'm only keeping 5g of fresh stuff on hand and I have it in one of those drinking water bubbler jugs with kalk. I don't like the idea of big storage if it isn't needed because even food-grade containers can leach hormone disrupters like BPA and phthalates. There have been rumors of nutrients leaching too but I think when tested those didn't pan out, or the bins were left in the sun or something. Like, I'd rather drink fresh tap water than something that's been in a trash can for a month, but I'm not a fish Also, I'm space challenged. Obvi is not a major concern since everyone's been using bins forever, but that's imho.

[reef_aholic]

[*]How does a closed lid brute container in a garage containing RODI water increase the TDS of the held water? Is there anything that I can do to prevent it?

If you use the same pail to move fresh RO/DI from brute to Salt mixing brute, the salt creep on pails can increase the TDS.

[fixedpoint]

Very good point. Does everyone else use a dedicated RODI pail?

[shifty51008]

If the container isnt air tight stuff can get inside and raise the tds. That being said as long as my tds was 0 going into my containers i dont worry about what the tds is in the container.

I use a pump to pump my rodi water to my sw mixing tank if i need it in a hurry otherwise i just let the rodi unit fill it up

[CStrickland]

I was reading about rodi setups this afternoon (I just finally switched over from tap water so I'm sort of into this lately) and there is something about excess CO2 degrading membranes that you might want to look into. Its not a problem I have so I didn't really get my head around it, but it reminded me of this thread. Maybe give that a Google?

[shifty51008]

the excess co2 uses up the DI much faster but don't think it causes problems with the membrane

[CStrickland]

Ah. K nevermind

[fixedpoint]

I cleaned the container with bleach, then vinegar, then tap water, and finally RODI water. The output from the DI unit is 0.2 ppm TDS. The water in the container is now 0.3 ppm TDS. Much better. Now, I'll let it sit for a few days and remeasure.

[ericarenee]

Originally Posted by fixedpoint

then tap water,

This was a Bad idea Depending on what is actually in your tap water..

[shifty51008]

Originally Posted by ericarenee

This was a Bad idea Depending on what is actually in your tap water..

I think he rinsed with rodi water after the tap, but even so when i clean my containers i use tap water and dry it out with a microfiber cloth and never had issues

[fixedpoint]

Yes, I dried after the tap water rinse with microcloth then RODI wash and dry. I was just concerned about residual bleach or vinegar, so I did a thorough cleaning.

[fixedpoint]

Took another reading -- 0.3 ppm TDS holding steady. Looks like the problem is resolved. Thanks everyone.