TDS question

[Auston]

Is 14 TDS before my di resin too high. Am I looking at a short life on the resin?

[swanny]

Perhaps but let's wait and see
K

[CStrickland]

What is your tap tds, pressure, waste ratio, and temperature?
Has it always been 14, or is it coming up?
Is it 14 right when you start, or after you clear the tds creep?

[Auston]

What is your tap tds, pressure, waste ratio, and temperature?
Has it always been 14, or is it coming up?
Is it 14 right when you start, or after you clear the tds creep?

Tap is 380ish, pressure no idea, waste ratio no idea. Temp is probably 8 Celsius. It's always been around 14. I just got the di today.

[mr_anderson]

In general, the pre-filters are there to remove "big" sediments and protect the membrane. The membrane does all the work, and depending on the efficiency, removes 97-99%. In your case, if 97% efficiency = 380 X 0.3 = 11.4. Your readings are 14. So yes, it is too high.

[CStrickland]

Tap is 380ish, pressure no idea, waste ratio no idea. Temp is probably 8 Celsius. It's always been around 14. I just got the di today.

Just to be clear, your not testing the first water that the unit makes right?
When it sits with water in it the tds "creeps" over to the other side of the membrane. So you want to let it run a few minutes to flush that out before you test it.

To get the best performance out of a rodi, you kind of have to work backwards. The di needs the membrane working well, the membrane depends on the prefilters, pressure and ratio, etc. Waste ratio is really easy to measure, you just see how must product water and waste water it makes in one minute. If your unit doesn't have a pressure meter idk.

8 Celsius is very cold. The gpd is based on 16 degree water.

[Auston]

Thanks for the info I'll get my unit looked at by my very knowledgeable lfs guy. He said he can do a full tune up for me. Do you guys have a bypass before your di cartridge?. That way you can bleed it off before you hit the resin.

[scuzy]

Mines around 10tds before resin and 0 after

[Nick92515]

I would also get a pressure Guage so you know if your giving enough pressure to properly preform.

[dkeller_nc]

Tap is 380ish, pressure no idea, waste ratio no idea. Temp is probably 8 Celsius. It's always been around 14. I just got the di today.

I'd suggest moving the unit to a location that's a bit warmer. If it's that cold simply because the incoming tap water is chilled, then you can add 20-30 feet of 1/4" polyethylene semi-rigid tubing between the tap water connection and your unit. Presuming that the air temp in the unit's location is 20 deg C or so, the length of tubing will give you a 5 deg C or more bump in water temp.

That will considerably improve your RODI unit's production rate, and it may also affect your TDS readings. The water coming out of the RO membrane won't be any more/less pure, but because conductivity is affected by temperature, and most units that hobbyists use aren't temperature compensated, you can get an impression of the unit's performance that's a bit off.

[CStrickland]

Thanks for the info I'll get my unit looked at by my very knowledgeable lfs guy. He said he can do a full tune up for me. Do you guys have a bypass before your di cartridge?. That way you can bleed it off before you hit the resin.

That may help if the issue is with the unit itself, like the membrane is not working correctly. But if it due to something at your house he won't be able to replicate it at the shop, diff pressure, temp, etc.
I just take of the di can and collect the water for my fw snails who need a gallon of ro a week any way.

[yoki32]

Does the coldness of water affect the effectiveness of the RODI machine? I live in Canada and my tap water is super cold atm so I'm wondering...

[CStrickland]

It affects the efficiency of the machine. The cold water is denser, so more is wasted instead of going through the membrane. My production rate slowed to a trickle when winter came. The water is not dirtier, you just waste more to get it.
And like DK said, if the water you are testing is very cold you need a tds meter that accounts for that. Maybe you could just let your sample sit a few minutes until it's room temp?

[vanbro1]

Check your pre filters and membrane. Don't want to burn the Di prematurely that's what ends up costing the most

[shifty51008]

The coldness effects production rate.

To me it sounds like the membrane is shot. My tds of tap is 534ppm and ro water is 3ppm useing a maxro membrane from buckeye hydro. But you are gonna want to add a pressure guage to your unit, you want at least 60 psi going into the membrane. A tds meter and pressure guage are a must on rodi systems as it tells you when to change your filters

[outssider]

Do you guys have a bypass before your di cartridge?. That way you can bleed it off before you hit the resin.

yes

[shifty51008]

Do you guys have a bypass before your di cartridge?. That way you can bleed it off before you hit the resin.

I do. if I didn't and when I start up the system I would have over 300ppm of water going into my DI which would kill it fast. I will bleed my RO water for about 3-4min before letting it go into the DI stage, by that time it will have dropped to around 4ppm.

[Member No. 1]

Is 14 TDS before my di resin too high. Am I looking at a short life on the resin?

Are you on well or city water?
Reason I ask is because another thing that will exhaust the DI resin quick is the co2 in well water. I have this problem. You need to off gas the co2 before it goes through the DI.

Here's how I do it.
http://www.reefcentral.com/forums/showthread.php?t=2548783