Furious with my RO/DI! Any help would be appreciated!

[hansnfrans]

I burned up 1/3 of my new DI resin after only making 25gal of water!!!!!!!!!!!


I have 3 pre-filters, then my booster pump and pressure gauge are between the 3rd pre-filter and my 100gpd RO membrane. It then goes to my DI canister.

My hand-held TDS meter was just recalibrated yesterday. I am on well-water. The TDS after the iron filter and water softener, but before my RO/DI unit is 768ppm. The TDS after my RO is 92ppm. The TDS after my DI is 000ppm.

My well pressure is 45psi and after the booster pump it is 88psi.

[c0mp|ex]

A water softener will raise TDS by adding salt to the water. You might want to invest into a second membrane. Also, how old is your current membrane? It might need replacement.

[fppf]

I found the 100 GPD membranes don't reject as well as the smaller ones.

The highest output I will go is 75 GPD
My 75 has an output TDS of around 10ppm
When I had a 100 GPD membrane I was seeing 30-50ppm

Softwater actually helps the RO membrane, a little salt is good, a lot of salt will damage the membrane however.

Also, why is your booster between prefilters and your membrane. I would think you want your booster before any filters.

In any event, sounds like the membrane is roached.

[Arthur1]

A couple of quick things for you first to start with, the rejection rate on the 100 gpd ro membranes is not really as good as say a 75gpd membrane. Water temperature as you may know also plays a role on water production. To get back to the main question in your post, possibly the amount of CO2 from the waell water is adding to the reason you're "smoking" your di filter. An ro membrane with a better rejection rate will of course also help to keep your di resin longer. Check your rejection rate to water production ratio and if you can, get a kit to test the CO2 level from your tap. HTH, at least a little

[hansnfrans]

Sorry, I forgot to mention that the 3 pre-filters, RO, and DI are all brand new and this is the first 25gal of water that I've made with these new filters.

[hansnfrans]

I was looking around and found the same thing you all did in reference to the rejection rate of the 100gpd membrane. I can't believe it only has a 90% rejection rate. That isn't a big deal for someone on city water, but for me here on well water, that's a lot o' TDS! Anyway, I purchased a couple 75gpd membranes from the same vendor that I ordered the 100gpd membranes from and I sent a request to return the 100gpd membranes because the one I hooked up was giving me ~88% rejection rate and not the advertised 90% rate. Hopefully they will refund the $ to me.

I am going to see about running 2 75gpd membranes in-line. With 770ppm TDS in my source water and ~98% rejection rate of the 75gpd membrane times 2, I should be down to ~0.31ppm TDS before the DI. But I will believe that when I see it. I also have purigen sitting around and am really considering buying another DI housing and running Purigen post DI.

I know the Purigen would be more useful running on my tank, but a filter floss that would keep the Purigen from escaping the reactor, will clog up after a few hours in my experience. So it's just sitting around.

[webfinger]

Second on the water softner. maybe try to pull your supply to your RO/DI prior to running it through the water softner. Also at 700+ and 98+ TDS at those locations you are going to burn through filters fast. My first stage only lasts for about 250 gallons because I have a lot of sediment but after my RO I'm at 0 TDS even before it goes into the DI. My incoming water is at about 500 TDS. Pressure is about 90 psi, pump prior to filter unit.

Also my rejection rate is huge as well. Claim on the unit is 1:3 but seems closer to 1:10.

[dipan]

With a TDS that high it is kind of critical that you get the highest rejection rate as possible out of your membrane. If you're interested in consuming as little DI resin as possible, that is. Rather than change the whole setup to twin membranes, why not consider spending a bit more on a tested higher rejection rate membrane from Spectrapure?

This one, with matched flow restrictor, has a 98+% rejection and 90GPD ...



$45 ... a bit more than a regular membrane + restrictor, but probably worth it in your case. Plus, it goes without saying that you have to make sure you regularly flush the membrane with an input TDS that high ...

[hansnfrans]

I am returning the 100gpd membranes in exchange for a couple 75gpd membranes with 98% rejection rate (Dow Filmtec). I am now using a fresh 75gpd membrane that went from a 98% rejection rate to a 93% rejection rate after only making 75gal of water, so, I will be putting up another thread here to find out why that might happen...

[dipan]

Another idea is to get one of those auto-flush valves and use it instead of a restrictor and manual backflush valve. This would help to ensure that your membrane get's rinsed regularly when in use. I'm using one of these right now with a booster and 75GPD membrane. Granted my incoming TDS is less than 300. It would probably help keep your membrane from getting less efficient as you are describing. Give Russ a call at Buckeye Field Supply if you're interested.

Also, how exactly are you calculating rejection rate? It should be 100 - (permeate TDS/tap TDS) ...

[hansnfrans]

The way that I calculated the rejection rate was taking my TDS reading post-membrane divided by my TDS reading pre-membrane, minus 1.

I am definitely getting an auto-flush valve, but the thing I have to figure out is if I can use one to flush out 2 RO membranes that run in parallel. As I will be hooking up a 2nd RO membrane in parallel this week when my parts arrive here. I don't really want to have to buy 2 of those auto-flush valves.

[LPS_Blasto]

Originally Posted by fppf

Also, why is your booster between prefilters and your membrane. I would think you want your booster before any filters.

I was told you don't need or want the booster pump slamming 80psi through your sediment filter and carbon blocks. It's fine to run normal house pressure through those first stages of the filter, and only boost the pressure before it goes into the RO membrane.

I have a 6-stage RO/DI unit from Filter Direct and I purchased it with a booster pump because my old apartment only had 30psi water pressure. I've since purchased a home and never bothered to check the house pressure. I just left the booster pump installed.

My booster pump is installed just before the RO membrane.

Maybe somebody with more experience can chime in about this?

[das75]

wondering how you determined that you exhausted 1/3 of your resin

[Arthur1]

Das, long time. Going to take a guess that it's color changing di resin and for whom the individual that mentioned it..you can run your booster pump before the sediment and carbon filters or after the carbon right before the membrane as the ro membrane is what is need of a higher water pressure in order to function correctly. HTH

[unbelievable]

U must really bed mad at your unit. LOL. I think u posted this in every forum I know of. Haha. Hope u get it figured out.

[tom obrecht]

Originally Posted by Arthur1

To get back to the main question in your post, possibly the amount of CO2 from the waell water is adding to the reason you're "smoking" your di filter.

I think Aurthur is right.

I 'm no expert but I too had super high tds well water (1500 plus!) and talking to Spectrapure they said co2 is a main factor of di usage. You might want to give them a call and see what they say. I actually set up a degassing stage before the di cartridge for this reason. Good luck!