RODI Problems

[Anonymous]

I have a brand new (2 month) RODI unit that is giving me trouble. Its only used for topoff water (I use NSW for WCs) and it is running through DI resin at a fast pace. I have changed the DI 3 times, and the last time I monitored water production- since then its made less than 200 liters (50GA) and the DI is nearly all depleted now.

The unit was run in properly, and makes water about once a week to fill my topoff reservour from where the water gets pumped into the sump on an automated system. The reservour topoff has two float switches and runs on a relay.

Any thoughts? TDS is zero when the resin is new, when it has changed colour, the TDS starts to climb to around 11 ppm.

 

[Anonymous]

Whats the TDS before the DI resin?

 

[Anonymous]

Dunno, the filter has a built in TDS reader that takes readings after the DI and then after the Kalk chamber. I am looking for a photo now for you.....

 

[Anonymous]

There it is- the TDS meter is obscured by the skimmer cup. Also visible is the Relay that a friend built for me....

 

[Anonymous]

We need to know the TDS of your source water. If its high, the DI exhausting is just doing its job. If its low we can look for other issues.

 

[Anonymous]

We need to know the TDS of your source water. If its high, the DI exhausting is just doing its job. If its low we can look for other issues.

I will try and borrow a portable TDS meter and test source and post RO water TDS in the next few days. The DI shouldnt be exhausting after only 50 GA, should it? Not after going through an extensive RO process- 2 X 5 micron partical filters, carbon, then a new RO membrane. Its confusing me a bit. Also, source water is not likely to be the problem, I got near 8 months out of my old DI filter at the apartment- and thats close enough to the new place to be on the same water system. That filter only had one 5 micron filter on it too!

 

[Anonymous]

Perhaps you have a bad membrane. Check the tds before and after your membrane. Your readings should be quite low after the RO membrane. If the membrane is faulty, you may be relying too heavily on your DI.

Dumb thought, but you do have your DI plumbed after your RO membrane? Perhaps some of the lines got put together improperly when you set this unit up on your new system.

 

[Anonymous]

Dumb thought, but you do have your DI plumbed after your RO membrane? Perhaps some of the lines got put together improperly when you set this unit up on your new system.

Thats an interesting perspective! I didnt think to check that, Thanks Mitchell, will look in the morning when I get home.

 

[Anonymous]

Checked the piping, its 100% correct. I have arranged for a portable TDS meter and will check either side of the membrane this weekend. I think I need to organise a new one just in case. Thanks for the input!

 

[Anonymous]

Checked the piping, its 100% correct. I have arranged for a portable TDS meter and will check either side of the membrane this weekend. I think I need to organise a new one just in case. Thanks for the input!

Good.

I'm betting on a faulty membrane. You should not be exhausting your DI resin so quickly as a final stage in RO production.

 

[Anonymous]

I assume you're using this for drinking water as well?

 

[Anonymous]

You should not have to wait for the portable TDS since all you have to do is to move the sensor after the DI to the spot between the DI and the RO, and take the reading.

Now you said you got 8 months out of the old filter and only 50 gal out of this new one.... you don't happen to only use 50 gal of DI in 8 months when you were in the apartment, do you? I don't remember how big is your old tank.

Looking that the quality of your tank equipments and how much effort you put in it, I am surprised that you are using that type of DI cartridge. You may want to replace one with a higher capacity, IMO. How many gram of resin does it hold?

 

[Anonymous]

You could pull the filter cartradiges and put the empty housing back on and run some water through it to get a TDS reading.

 

[Anonymous]

Mitchell, I am also of the belief that its a daulty RO membrane.

7E, my other tank was near 400GA so it used a lot of water, 80 liters would have been less than a week's worth.

Craig, I do filter my drinking water, but with a far larger unit that just does particle and carbon. Its not on this system.

Mark, I will make a plan, my resin is exhausted already, I will throw it out and leave the chamber empty, take a reading, then remove the membrane and take another reading- that should provide a pre and post membrane reading. I suspect they will be identical.

 

[Anonymous]

Craig, I do filter my drinking water, but with a far larger unit that just does particle and carbon. Its not on this system.

Gotcha. I was wondering about the uppermost horizontal chamber in the pic above. I had a similar unit in Taiwan, bought at HD as a "drinking water RO", it came with a chamber filled with some stones (quartz? marble?) that made the post-RO water more palatable. They raised the TDS, but made the water taste less like distilled.

Of course I'm not trying to insult you by pointing out the obvious, just looking for the easiest solution. :mrgreen:

So what the hell is in that top tube?

 

[Anonymous]

Its Kalk, in granular form. I dont think it makes much difference on a system my side, and I dose top-up through a kalkstirrer anyway. It does add about 20ppm to the water- the TDS meter measures pre and post that chamber, so the effectiveness is there- just not in volumes enough to supply a system which shortly will be approaching 8000 liters (2000GA) (When I finish rebuilding my old tank and plumb it into the new sump)

 

[Anonymous]

FWIW, I won't call it kalk. It is calcium carbonate. It very insoluble, as you noticed.

 

[rbursek]

I am confused I think, that upper horizontal chamber is filled with Kalk or is that your DI resin chamber? If Kalk is that after or before your DI and meter? If it is before your meter the Kalk is adding TDS's. If DI resin, in horizontal chambers the resin does not get all exposed to the water running through it before you get high TDS readings.

 

[Anonymous]

The white plastic on the very top is the aragonite post-filter (add calcium and carbonate to the RO/DO). The clear plastic one with two round blue endcaps is the DI housing. The aragonite filter should be after the DI stage. Even if it was misconnected, and go before the DI, it should not kill the resin like he did.

 

[rbursek]

Got the set up! So you have a horizontal DI canister, the water is only travelling through the lower half of the DI resin, try and mount it vertically with the inlet on the bottom and outlet on the top.