ro/di tds

[jitterbug]

so I got a new ro/di unit (well new to me) and I have a quick ? On it my tds meter reads 297 tds going in and 12 tds coming out is that good? The guy that I got it form told me that he changed the filter about 3 months ago the di chamber is hafl black

thanks for your input jr.

[franklypre]

new filters will help, prefilters and RO membrane and DI refills.

[AZDesertRat]

You need three TDS numbers to determine the condition of the RO membrane and DI resin. Prefilters and carbons have very little to absolutely no effect on TDS so you change them at 6 month intervals or when you detect a significant drop in incoming pressure.

 

You have your incoming or tap water TDS and what I assume is your final RO/DI TDS but you also need your RO only TDS. This will tell you how the membrane, the workhorse of the system, is doing. If you don't havbe a DI bypass valve, disconect the line from the RO to the DI at the DI end and sample from there.

 

Buying a used RO or RO/DI is a crap shoot at best. You should always look at it as if you are buying housings only as the filters probably need servicing. You say he replaced the filter 3 months ago, do you know which one or ones? Do you know what RO membrane it has, is it a Dow 75 GPD or maybe a 100 GPD which is not nearly as efficient? Does ot have color changing DI resin? If not colors mean nothing, it could just be the cartridge was not packed tightly as is stratifying or seperating in layers of anionic and cationic resins.

 

Don't buy anything until you know what you need first, you could be throwing money away.

[Byrdman]

i would try changin the membrane. My prefilters are 5 months old and the DI is nearly spent less than half black and its still 0.

[AZDesertRat]

DO NOT change anything, membrane included until you know where the problem lies. Do not rely on color changing DI resins either, they may change is streaks, bottom to top, top to bottom , not at all, all at once, etc, very unreliable. Resin usually turns colors too late and you are already passing weakly ionized substances like phosphates, silicates and nitrates, even before it is exhausted. Use a handheld TDS meter and use it often. Chances are if a DIcartridge is half black it is not packed tightly and the resin has seperated into cation and anion layers, this is very common. Always pack a cartridge tightly, tap it on the counter or table several times, add more resin, tap it again then add the donut to fill the void.

[jitterbug]

its a 50gpd membrane. So if I get a new membrane and housing and change the di resin will that help? Bulk reef has a 75gpd membrane and housing for like $50. What do you guys think.

 

thanks jr.

[AZDesertRat]

What is your RO only TDS? That is what will tell you if you need a new membrane or not.http://www.spectrapure.com/email/customer-appreciation.html#1

If you do need a new membrane, batch tested and treated RO membranes are on sale for $30 here:

http://www.spectrapure.com/email/customer-...eciation.html#1

at up to 90 GPD, all you would need is a $5 flow restrictor to go with it and you now have a 90 GPD system. Check your TDS first though, you may not need one, it could just be bad or exhausted DI resin.

[jitterbug]

ok I will test the ro only what # do I want ?

[AZDesertRat]

90+% less than the tap water TDS. A properly functioning membrane should remove 96-98% of the incoming TDS. If its much worse than that DI replacement costs go up significantly and soone exceed the cost of a replacment RO membrane. For every 2% you decrease the membranes efficiency you cut your DI life in half so even the difference between 96 and 98% is significant.

[jitterbug]

Ok so i just tested only the ro (no di) and the tds was 25-28 tds on the out side and on the in line 290 tds. what do you think azdesertrat?

[MEDGE]

to calculate the rejection rate of the membrane you take the tap water tds minus the tds after the membrane, divide by the tap water tds multiply by 100

 

So in your case:

 

[(290-28)/290] x 100

 

= 262/290 = .9034 x 100 = 90.34

 

Total rejection rate from your membrane is 90 percent.

[AZDesertRat]

90% rejection is pretty low, remember I said for every 2% decrease in efficiency the DI life is cut in half.

The inverse is for every 2% you increase that rejection rate or efficiency you double the DI life so a new 98% rejection rate membrane would make DI last much much longer and pay for itself quickly. Spectrapure has 98% 90 GPD batch tested membranes for $30 right now.

http://www.spectrapure.com/email/customer-...eciation.html#1

[krug1313]

Just finally got my new ro unit hooked up. It doesn't have DI but I'm adding that on soon. My tap water was 140 ppm and after running through ro it's down to 13 ppm. This is a safe level to use in my tank correct? At least until I order the DI stage? It might even come down as I'm just running the water down the drain at the moment since all filters etc are new.

[AZDesertRat]

Much better than tap for sure. It will probably come down a little bit more as the membrane seasons but I would add the DI when you get a chance for 0 TDS water.

 

RO or RO/DI are cheap insurance.

[krug1313]

For sure.. I was happy not to buy jugs of water then went to hook it up and none of the fittings would fit..lol. So had to buy a jug of water..lol.. After many calls around town I tracked down a saddle valve and I'm in business..lol

 

just tested tds @ 9ppm now.

[geewiz]

really save some money and learn to recharge you di resin!

[AZDesertRat]

Recharging resins requires you keep the cation and anion resins seperate and also requires hazardous chemicals like lye and acid. Not worth it to me plus you can never rechage it back to 100% strength at home. Resin lasts a long long time with a quality RO membrane and is relatively inexpensive.

[geewiz]

Recharging resins requires you keep the cation and anion resins seperate and also requires hazardous chemicals like lye and acid. Not worth it to me plus you can never recharge it back to 100% strength at home. Resin lasts a long long time with a quality RO membrane and is relatively inexpensive.

 

drain opener and brick cleaner. i don't even wear gloves. but sure i would suggest that one wear protective eye wear. these chems are sitting in your kitchen and bathroom cabinets right now some even in greater strength. mom grabs them and cleans the toilet, bathtub, etc.

 

i have the cation and anion resins in separate filter cartridges like what is done commercially for recharge ease. with my current setup it takes me about 5 minutes to recharge. remove resin in bag, place in bucket of di water and acid or lye, rinse well in di water. replace into cartrdge.

 

i haven't bought di resin in over 5 years. so money well... not spent. i run it with a quality ro membrane, a seven stage system. but really thats because i was in the filter business back when. why do electronic companies, car washes, labs etc. use only resin and recharge? because its more efficient and cheaper than using a ro membrane. but that wasn't my point. my point is learn to recharge.

 

oh and btw some msds for test kits. are they too hazardous and not worth it to you?

 

Causes severe burns.

Risk of serious damage to eyes

Toxic by inhalation.

May be harmful to the fetus/ embryo.

Danger of cumulative effects.

iritating to eyes, respiratory system and skin.

Eye contact may produce serious damage.

Ingestion may produce health damage.

 

my favorite is harmful to fetus, fun stuff.

[AZDesertRat]

Working in water treatment plants I am around those chemicals every day. I don't choose to work with them when I get home. It can be done but again is not as efficient as new resin and you will find seperate anion and cation canisters can and will mess with the pH of the effluent.

[geewiz]

It can be done but again is not as efficient as new resin and you will find seperate anion and cation canisters can and will mess with the pH of the effluent.

 

if you are not getting below .5 tds more than likely you are not neutral ph. your point is notable but moot.

[AZDesertRat]

Its not moot, seperate resins can cause acidic waters. Thats why most mixed bed resins are not a 50/50 mix of cation anion.

[geewiz]

Its not moot, seperate resins can cause acidic waters. Thats why most mixed bed resins are not a 50/50 mix of cation anion.

 

wrong separate resins can cause alkaline waters or acid waters. it depends on the resins. but the point is rather moot about your acid water because most if not all quality color changing nuclear grade aquarium di resins are i'm most sure, always strong base so you will be a ph of about 8.5 not acid if using only di resin (no ro) and have them separate. but still its all ridiculous because more than likely the di water we are producing is in the 10+ megohm range which is pretty darn close to a neutral ph no matter which side of 7 it fluctuates.

 

but regardless i wasn't trying to discuss all this ph crap. my point was about your statement that recharging di resin is hazardous and recommending that people don't do it. when, test kits are as or more hazardous. your statement that it requires keeping them separate is wrong though it does make it easier. furthermore, while one cant recharge it back to 100%, that does not mean that it does not work as well, it only means that it wont last as long between recharges. after 5 years i have to recharge about every 3 months.

[AZDesertRat]

I am getting 18+ megaphms with my DI, If I only got in the 10 range I would not be happy at all.

Ragardless, the average person is not going to want to recharge resin at home, its a PITA. Been theer done that and not worth it for me.

[geewiz]

I am getting 18+ megaphms with my DI, If I only got in the 10 range I would not be happy at all.

Ragardless, the average person is not going to want to recharge resin at home, its a PITA. Been theer done that and not worth it for me.

 

it's all good.