some help with RODI

k, heres whats going on.
i have a 75gpd rodi set up, 3 pre filters, running air water ice set up of 10um,5um,1um, and plus the DI, making it a 5 stage syster, with a 4 gal diagphram storage tank, (we also use this to make just RO water for personal drinking.

so theres a couple questions:

1. i turn on the main valve, and let the tank fill, as it pressurizes, the auto shut off valve should, turn off the flow to the filters, but itstead it starts vibrating, rattles all the plumbing in the house, wont stop till pressure in the system is dropped, i.e. turn on a faucet, flush a toilet, turn off main valve to the filer.

2.once the rattling starts, i turn off the main inlet, and if i let it set over night, i lose all water out of the storage tank. could it be going back thru the filters and out the waste line? would a backflow preventer stop this?

3. i pulled the membrane out of the holder, to see what gpd it was, (couldnt remember), put back together, now, i just ran water into the 30 or so gallan rubbermaid i use to make up water change water, and it usuall takes most of the day to fill, after an hour or so, the tub was overflowing, and when i pulled the hose out, it was free flowing, and is usually a fast drip, and my tds meter says my tds is at 4ppm, and is always 0ppm, incomong is 41ppm steady.

so, what do you think i could have done just by pulling the membrane out and putting back in?
why does the tank empty?
why do my pipes rattle?

i have new filters, membrane, and auto shut off coming from air water ice, and im going to repost this in their sponsor thread.

any help is appreciated

thanks

Rayn

 

Are you sure the RO/DI system has an auto shutoff? If not then the system will not shut off on its own. Or if there is one it could be faulty. And I would think if there was no auto shut off valve then yes, the bladder will push the water back through and could damage the unit.

As for the membrane, it sounds like it isn't seated correctly. Try removing it, inspect all the o-rings, and reinserting, be sure to seat it all the way into the housing (they always seem to go deeper than you would think).

Also for the bladder, do you have it tee'd in between the RO and the DI canister? You don't want to store the DI water in the bladder.

 

thanks for the reply.
it has one of those auto shut of valve, with the 4 ports on it, and it never really worked right, i got the base sys used, then added the tank and DI.
so yes, looking at it, the water must be pushing back through the membrane to drain, only place for it to go, so i need a backflow preventer as i thought.

im going to pull the membrane out and check the o rings and seat, must be the problem, but i have a new one on its way so may not worry about it.

yes, the bladder is tee'd between the ro and di, i have 2 hoses coming off the unit, one after the DI for tank water, and one between the bladder and DI that i use for drinking water (save a ton of $ on bottled water, and no plastic bottles for the planet)

 

Does the water come out of RO then into bladder, then to DI? The rubber bladder tank will add TDS to the water and exhaust the DI very quick.

 

yes, exactly.
im not real worried about exhausting the di, i like the storage capability, and my tds are always at 0 coming out of the DI, until now.
i cant get a line from the filter to the the refugium for an ATO set up, but might pick up a second system that will fit under the sink then plumb to the fuge

 

I would find a schematic to that system with the auto shutoff on it and double check to see if you have all the hoses going to the right places. I had that same problem when I had my first system that I bought off a reefer and he told me it was plug and play and it ended up being plug and bust. If you did already then I apologize.

 

I got the sys off Craigslist for $10. Put in new filters and added the di and tank.
I researched the plumbing for it then, I'm pretty sure the aso is plumbed right and never worked right. I have a new one coming from air water n ice on Tuesday so hopefully it has directions

 

Mine does the same thing but does shut itself off without any outside help. Make sure your system has the check valve on it I believe after the auto shut off

 

It has no check valve anywhere. I have one comingnthough

 

Remember that RO membranes function based upon the difference in the pressure on the feedwater side of the membrane versus the pressure on the storage tank side of the membrane.
So for sake of discussion let’s say you have 50 psi tap water and your RO water goes to a 5 gallon bucket at 0 psi. So the membrane is operating at 50 – 0 = 50 psi net driving pressure.
Now, if you have your RO water delivered to a pressurized tank, when the tank is full it will provide pressure back against the membrane at 66 to 85% of the feedwater pressure, so 50 psi - ~38 psi = 12 lbs of net driving pressure. You can imagine what sort of rejection rate you’ll see at 12 psi.
So the TDS of RO water in a full tank will be substantially higher than the TDS in RO water delivered to an atmospheric (unpressurized) tank.

Now – Can an RODI system be plumbed and configured appropriately to include a pressure tank? You bet. Our Reef/Residential Series Systems are an example.

Russ