I have been looking through AAMI to find what the final water conductivity should be after the Ultra-Filter. Any idea's as to where I might find this or is there such a thing. I've found where the RO should be greater than 90%, but nothing on Fianl water conductivity.

GLRNTech,

There is no limit for conductivity as long as the water meets the standards.

Chuck

There is also no limit for % rejection. I don't know where you found 90%. The % rejection can be 50% and this be acceptable as long as the water meets the individual chemical limits listed in AAMI. 90% is an routinely accepted limit for % rejection, but there is no REQUIREMENT in AAMI. There is a suggestion in RD52 to send a water sample in for analysis if the % rejection falls below 90%.

Keep in mind that conductivity measures ions in the water. The limits for some of the individual chemicals listed in AAMI are very low (i.e. Beryllium <0.0004 mg/L). If your conductivity is 50 and your Beryllium is 0.0003, you have acceptable water. But if your Beryllium increases to 0.0005, you wont see much of a change in conductivity but your water will not be acceptable.

I have been looking for that also with no solution. SO if your machine is running 95% rejection and then slowly drops down below 90% and your TDS goes above 50 ppm, do you stop using the machine until an acceptable AAMI test is returned?

Are you saying there are no specific limits from AAMI that a user can go by to determine proper water quality just by reading the numbers off the machine?

I have questioned this because your rejection can vary but incoming and outgoing TDS. ANd have not found a specific TDS number.

Chettrick, that is correct. As Florian stated, there is no AAMI limit for TDS or conductivity. The only limits established by AAMI are the levels for contaminates in the water that are tested when you do your annual AAMI water testing. If you have a machine that was running 95% rejection that slowly drops to less than 90% and the TDS goes above 50 as you said then depending on how your medical director feels you may very well have to stop using a RO unit until you get back a AAMI water anyalysis. It also would depend on what your water normally runs or if there had been some changes to the incoming water that caused the change. Around here the city changes water sources depending on the time of year and drought conditions. If it was me and I noticed the rejection dropping I would send off a sample before things got down below 90% rejection or above 50 TDS. Also depending on the age of the membranes I very well may order new membranes and replace them and be done with it. As you can see, and Florian may agree or disagree, there are alot of factors to figure in when it comes to water systems and their performance. Experience is definately a plus when dealing with water and if all else fails it better to act early and be safe than to wait and have something go wrong. Just my 2 cents worth.

Midwest states it very well, although I wouldn't necessarily shutdown the unit if the % reject falls or TDS increases...unless patients start having a reaction. Conductivity and % rejection are good ways to trend how your RO is performing. But, that is all they are...a trend. Some states require sending in a water sample if the % rejection falls below 90%...but you don't have to shutdown the clinic while waiting for the results. I have seen clinics that can meet the AAMI guidelines with the RO at 80% rejection, and I have seen clinics that do not meet AAMI when their RO is at 95% rejection. You have to determine the limits for your clinic. There is no guarantee. It is possible to take a sample when the RO TDS is at 50 and have it meet AAMI, and later take another sample when the RO TDS is at 50 and have it not meet AAMI. It is important to note any affect on your patient.

Also check out
http://renalweb.groupee.net/ev...011097504#7011097504

Be sure your medical director is signing off on what you do since he is the one ultimately responsible for the water system.

This discussion clearly illustrates the importance of logging your water system daily.
By doing this you can easily pick up trends and changes in the water. Very important to keep the physician in charge in the loop(so to speak).

Yes, this a very interesting discussion. What I see is that there no AAMI limits for rejection or TDS other than test results from an AAMI certified Lab.

It gets confusing sometimes when my main RO system never runs above 4 ppm even after 4 years. The feed water is 330 ppm and we only do the ph cleaning once a year and minncare every 6 months. Not because test results show we need it but as a preventative. IT runs the water through a media filter, then softner and then two carbon tanks before a 1 micron filter then membranes. It is producing at least 500 gallons a day.

I have 8 portables, same manufacturer. (Osmonics/Zyzatech/GE/Marcor). The best these have ever run right after membrane replacement is 4-5 ppm, then over a couple of years it crawls up to 50ppm. They also run on the same series of filtering but on smaller scale, and the usage is a lot lower. The percent rejection stays with it and our feed does not seem to change much from time to time when I test it, which is the same feed water as the main system.

They are all designed with an alarm that is settable to 5,10,20 and 50 ppm. The only thing I found in AAMI standards is that it has an alarm that indicates something.

So if my percent rejection is 80-85% and TDS is above 50ppm and AAMI testing says that all my minerals are at good levels, I would have have to tape over the alarm switch to keep the audio off. Which defeats the purpose of the alarm standard but AAMI says the water is good.

If the rules are different across the country, then what is the director of a dialysis unit supposed to go by?

chettrick,
I'm not sure if I read it here or heard it in a water class but the rule of thumb I use for condo limits is doubling your baseline.
New membrane = 10uS product, then limit = 20uS. Of couse, only if 20uS is tested & within AAMI.
New portable = 5uS, limit = 10uS. If 50 is ok then obviously you can relax 10uS some but if your getting that much change in you product water condo, what's causing it? scale, temp, cal drift?
I use the limit to indicate that something has failed or its time for cleaning, not that its necessarily outside of AAMI limits.

GLRNTech, Do you work with Dr.V.Rozas?

This turned out to be better question than I was thinking. Thanks for everyones input. Florian, RD52 is where I picked up the 90% and that was the only thing I could find on percent rejection or anything on conductivity of the treated water.
Reason I brought this question up is that my clinical director has set a upper limit of 20 microsiemens. So anything above that she wants the patients removed and the water system checked out, I feel this is low. That puts my system to alarm at 95 - 97%. So I started researching and could not find anything. Except what RD52 stated.

Oldman, yes I did work with Dr. V.Rozas, he retired at the beging of this year.

Thanks everyone, this is very interesting.

GLRNTech, yes in my opinion that is too low. But as I and others have said, ultimately the medical director/physician has the final say. Hopefully your clinical director will be open to discussing this and be willing to let you raise your limit. Here our upper limit has been set at 40 microsiemens and once we reach that level, regardless of how the AAMI test come out, I have to replace the membranes.

Chettrick, you are fortunate to have good incoming water. Here, after pretreatment, the incoming water runs 900-1000 microsiemens giving us 6-9 microsiemen at 99% rejection on the RO's. Our system is also alot larger as we have the capacity to produce 600 gallons per hour. We clean the membranes as needed and disinfect monthly at a minimum. Good luck to all.

While we're on the subject, does anybody know how to convert micro siemens to TDS?

If 1ppm TDS = 1.56 mS/cm, you would multiply your ppm by 1.56 to convert from TDS to mS. Would you be able to divide to go the other way? i.e. 50mS/1.56 = 32ppm

Just a guess.