Has this ever happened to you? RO unit question

[ripped tide]

I changed the micron and the carbon cartridge of my RO unit last night. The last time I changed them was about 2 months ago. After back flushing and putting everything back together, I turned it on and monitored the flow of the good and the waste water lines. The good water line was flowing as it had before, but the waste was just barely dripping. The waste had been at a significantly noticable higher flow rate before. I pulled it all apart, cleared the lines, looked for debris, back flushed again but still no change. Is this just a result of new cartridges and producing much more usable pure water? Or is my membrane gone? It is only a 25gpd so rejection should be low. A drip per second seems too low. Any enlightenment?

 

[ripped tide]

I cleaned the restrictor last night, it wasn't too nasty. I back flushed again, seemed to help, the waste and the good water are close to the same rate.

 

[Jaycen B.]

Did you flush the carbon block before it was installed? I am also thinking a clog.
What brand unit do you have?
Is the flow restrictor inline or stuck in the end of the tube?

If it is the in the end of the tube I may have a new one you could try.

 

[ripped tide]

I pulled it all apart again soaked the restricter in vinegar, it's back to normal flow.

 

[buckeye field supply]

Just to help avoid confusion:

Ripped Tide;679267 wrote: I changed the micron and the carbon cartridge of my RO unit…

Sediment filters and carbon blocks have very small holes in them. So small that the diameter of the holes are measured in millionths of a meter, or “microns.” Best to refer to prefilters as “sediment filters” and “carbon blocks.” Really no such thing as a “micron filter.”

After back flushing and putting everything back together…

I don’t know of any systems that “back” flush – meaning reverse the normal direction of water flow. Some systems, include a valve to flush the membrane – but there is no “back” about it.

It is only a 25gpd so rejection should be low.

“Rejection” is a measure of the percent of the contaminants in the feedwater that the RO membrane does NOT allow to pass through to the purified water stream. So your 25 gpd membrane likely has a very high rejection rate – likely 98%. The higher the rejection rate of your membrane, the less work your DI resin has to do to lower the TDS down to 0 ppm.
Rejection can be calculated like this:
100% - (RO water TDS – Feedwater TDS). So if your tap water is 400 ppm TDS, and your RO water is 4 ppm TDS, then
100% - (4/400)=
100% - 1%=
99%
You’ll need a TDS meter to get the data to calculate your membranes rejection rate.

“Rejection rate” has nothing to do with the ratio of purified water to waste water. That’s referred to as “recovery.” Recovery can be calculated by determining the percentage of feedwater that ends up as RO water (a.k.a “permeate&#8221. So if you have a 4:1 ratio of waste water to permeate, you have a 1/5 or 20% recovery. High recovery may lead to a premature demise of your membrane, and low recovery may needlessly waste water.

Russ

 

[atlweb]

Do you have any advice on getting the cannisters off to replace to carbon, etc.? I have a spectrapure 4 stage RODI unit and no matter how hard I try, I can't seem to unscrew it. Maybe a wrench of some sort?

 

[ripped tide]

There is an RO canister wrench you can buy (I'm sure ol' Russ can give a technical name ;-) ). Check bulkreefsupply.com

 

[buckeye field supply]

"Universal housing wrench" is what you're looking for. Also make sure all pressure is rereleived from the system when you try to unscrew a housing, and also make sure you wash and lube housing orings. Use food grade silicone grease.

Russ