RI/DI problem

[Myka]

0.01 ppm? You're worried about that? I wouldn't be. However, I would be checking TDS after RO membrane before DI resin. When is the last time you changed the DI resin? Did you have the system apart at all or did this problem start on its own? Does it normally drain down in the DI chamber when you shut it off and refill when you initially turn it on or does it always remain full?

[Coleus]

I just changed the DI resin like 1 week ago, The problem just start yesterday, before it was find and I flush the membrane for 10 minutes the last time i used which was a week ago

It does normally drain down in the DI chamber half way and then refill when turn it on again.

[Myka]

Hmmm...mine does that too (draining DI chamber down partially) ever since I changed the DI resin. Before I changed the DI resin it didn't drain down. I refilled the DI cartridge that came with the system (AquaFX). I never did figure out what the problem was, and it has continued to happen ever since. I didn't pay attention very closely when I removed the cartridge since I didn't realize it is refillable I was going to toss it and use a different refillable cartridge. When I noticed the AquaFX one is refillable I refilled it, and put it back in. I thought that maybe I didn't put it back right or I dropped an o-ring or something, but I have no idea. It is almost like some of the water is somehow bypassing the filter. I really just don't get how it does it...I think it is sucking air in from the RO waste line when the system is shut off, but I haven't actually tested that theory. I can't think of any other way for air to get in there, and the water to get out. I also don't get any TDS so that doesn't make sense either. I sent photos and the same question to AquaFX and although they tried to help neither of us could figure out the problem. Since I get 0 TDS from it, I just ignore it.

[mike31154]

The DI chamber in my BWI 75gpd 5 stage system has never filled up since day 1. I get 0 TDS out so I don't sweat it. Sometimes it gets about half full after I've opened one of the pre filter housings or if I've run just RO for drinking water for a while. Doesn't take long to almost empty out once I start running the DI again though. I've read a few posts here and elsewhere with similar info, some saying it's normal. No clue how it works, but like I said, TDS 0, why worry?

[hillegom]

Maybe you could put a towel under it, slowly unscrew the cannister, until it fills and then retighten.

[albert_dao]

You don't really ever want to be running any of the canisters half full. It reduces the capacity of the resins/cartridges.

Check and tighten all your fittings.

[mike31154]

I can understand it being a problem if your pre filter or carbon block filter housings are not filling completely, but the DI stage on most systems is generally a refillable cartridge and it has openings only at the top & bottom, that is, the water can only enter and exit at the bottom/top since the rest of the filter is a non permeable plastic casing. Therefore, as far as I can tell, there shouldn't be a need for the DI housing to be completely full of water for it to work correctly. As long as there's sufficient water going through the housing to enter one side of the DI case and exit the other, I don't see the need to have the entire housing completely full. Carbon blocks & poly pre filters allow the water to permeate along the entire length of the filter, so yes, those housings need to be full for best performance. I'm just thinking out loud here and could be very wrong, but as I mentioned, I get 0 TDS out of my system and my DI housing has never been full. The resin is slowly changing colour from bottom to top which would indicate that the water moves from the outside of the cartridge, into the bottom of the DI casing and out the top. Pretty sure all the other housings work the same way as far as which way the water travels... from the outside of the filter, then through the center top to the next housing.

Having said that, I also had a refillable carbon cartridge between my 1st stage poly pre filter and my solid carbon block filter. I've since replaced it with another poly pre filter. These pre filters are always completely full and the refillable carbon filter looks to be the same type of housing as the refillable DI cartridge, so not sure why one would be full and not the other. Maybe because there's higher pressure at the pre filter housings before the RO membrane. I reckon by the time the water gets to the final DI stage, there's not a whole lot of pressure left. The pre filters, RO membrane and waste line bleed off a pile of psi. Makes sense that the DI housing may not fill up since there's such a slow output after both the RO membrane and out of your DI line. There's no back pressure there until your auto shutoff on the DI line kicks in, if so equipped. Quite certain all my fittings are secure and water tight, otherwise there would be bubbling or water leaking out somewhere with just over 80 psi source pressure and 60 psi before the RO membrane.

[Myka]

Originally Posted by hillegom

Maybe you could put a towel under it, slowly unscrew the cannister, until it fills and then retighten.

I have done that, and the water line just goes down again. What I don't understand is that from what I can tell, my DI cartridge works like a Phosban reactor where the water goes in the top of the cartridge and comes out the bottom of the cartridge, then flows up to the top of the chamber where it leaves the chamber through the top plate. That's what it looks like to me, so how the heck is there water coming out of that chamber when the outlet is as the top and the water level is only halfway up the chamber? I get about 12 ppm out of the RO, and 0 ppm out of the DI.

[hillegom]

Myka
I think it must work like mike31154 says. Water comes in on the outside of the DI canister and then exits up through the DI. That way, air cannot escape easily.
I think if you reverse the flow(don't know if its any better) to go into the top of the DI cartridge and exit the bottom and then out of the cannister, I do not see any possible way for air to stay in the cannister.

[mike31154]

Originally Posted by Myka

I have done that, and the water line just goes down again. What I don't understand is that from what I can tell, my DI cartridge works like a Phosban reactor where the water goes in the top of the cartridge and comes out the bottom of the cartridge, then flows up to the top of the chamber where it leaves the chamber through the top plate. That's what it looks like to me, so how the heck is there water coming out of that chamber when the outlet is as the top and the water level is only halfway up the chamber? I get about 12 ppm out of the RO, and 0 ppm out of the DI.

I don't think it works the way it looks like to you. I've never seen a phosban reactor, but am pretty sure most RODI system housings & tops are designed & built according to a generic standard. I think the water permeates the filter from around the outside (not the center) and exits through the core of the filter to the top. This would make sense particularly for the poly filters since the greatest surface area is the outside of the filter. It should be more efficient to push the water from the outer circumference to the smaller core. I can more or less confirm that since my 1 micron poly filter gets very gunky on the outside while the inner core is still fairly clean. Plus, it's unlikely companies would manufacture these generic/standard housings differently for a refillable DI or Carbon filter. Too easy to get things confused and mixed up.

I haven't taken a look recently, but if the refillable DI cartridge is built the same way as my refillable Carbon cartridge (which I took out a wile ago so I checked how it's built), then there will be slots around the bottom of the casing. Since the water can't permeate the sides of the plastic casing, it needs to enter these bottom slots and work its way up through the media then out the top center to the output. This should explain why there only needs to be a little water visible in the bottom of the housing. As long as the slots at the bottom of the refillable cartridge are covered, Bob's your uncle. There's likely sufficient air pressure in the outer housing to keep the water percolating up through the top of the DI casing and out. Again just thinking out loud and also trying to make sense of why this works without completely filling the DI housing. Would be nice if an expert from one of the RODI system sponsors could pipe in and provide clarification.