Pressure Drop on RO/DI

[Buzz1329]

The water pressure on my BRS 75 gpd RO/DI suddenly dropped from 55 to 35 PSI recently. I’ve had it for a little over four months for my 75 gal. DT and 30 gal. sump. I use it to produce about 25 gallons a week. Anyway, I swapped out the sediment filter and flushed the RO membrane, but it did not seem to make a difference. I notice that BRS recommends that you replace the carbon cartridges after a year’s use on a 100 gallon DT, but I’m thinking this is the next logical step. Any thoughts? Thanks,

[disc1]

Changing out the carbon would be my next move.

[gweston]

It could be the pressure of the incoming water from the town, and not as a result of the RODI unit. My pressure is usually around 43psi (in the winter). Since warm weather started, coming in, it slowly dropped to around 30-35psi. Making water is SLOOOOOOOOW. I even changed my sediment filter out. Zero impact. My membrane is brand new too.

I borrowed an RODI booster pump from a friend... instantly I was up to 75+psi and I made over 245gals of water for my new system over a few days using a 75gpd rodi.

I haven't bought a booster pump yet, but it is on the top of my list. If my pressure is 45psi or above normally though, I probably wouldn't look at a booster.

[Buzz1329]

Thanks for the quick responses! I'll swap out the carbon filters and if that does not do it, go for a booster pump.

[rayviv]

I believe that BRS states that 60lbs of pressure are required for that system to run properly and seems that that is standard. Not sure if making water quicker than say 75gpd in a system rated for less say 50gpd would cause higher TDS (total de-solved solids) reading but I would keep eye on TDS readings if you're pushing water faster by adding pressure.
Ray

[rayviv]

I notice that BRS recommends that you replace the carbon cartridges after a year’s use on a 100 gallon DT, but I’m thinking this is the next logical step. Any thoughts? Thanks,
========================================================
Ive run mine over a year and the local water company's TDS runs 433 - 600 at times. So I think that it depends on the tap water readings. I have gotten to where I let my TDS go to 10-12 before I correct it.

Do you know how to trouble shoot the different elements?

[Techbiker]

I only have 45 psi, never really care for the speed, but the TDS reader still show 0 coming out, is this what it really matters?


Sent from my iPhone because I am not home with my fishes

[rayviv]

Originally Posted by Techbiker

I only have 45 psi, never really care for the speed, but the TDS reader still show 0 coming out, is this what it really matters?


Sent from my iPhone because I am not home with my fishes

Yes... The TDS is what we are looking for. I think that slower production may help the different components last longer. At least it seems to be the case for me. Ive run mine for almost 18 mos and have not had to change any of the elements. And as of yesterday my TDS just went to 11.

I live in Huber Hts, OH and the water from tap is at 433 as of a couple days ago. We get a water info letter from water comp. every 6 mos. and I just got
mine.

Now let my say this loud and clear; I am novice and can only speak on what seems to be the case with my RODI unit. I think I have it for 5yrs.
Ray

[Buckeye Hydro]

Originally Posted by disc1

changing out the carbon would be my next move.

+1

[Buckeye Hydro]

Originally Posted by gweston

It could be the pressure of the incoming water from the town, and not as a result of the RODI unit. My pressure is usually around 43psi (in the winter). Since warm weather started, coming in, it slowly dropped to around 30-35psi. Making water is SLOOOOOOOOW. I even changed my sediment filter out. Zero impact. My membrane is brand new too.

I borrowed an RODI booster pump from a friend... instantly I was up to 75+psi and I made over 245gals of water for my new system over a few days using a 75gpd rodi.

I haven't bought a booster pump yet, but it is on the top of my list. If my pressure is 45psi or above normally though, I probably wouldn't look at a booster.

With pressure that low your system just won't work worth a darn. Slow production, too much water going out the waste tube, reduced rejection, and short DI life span:



Russ

[Buckeye Hydro]

Originally Posted by rayviv

Ive run mine for almost 18 mos and have not had to change any of the elements. And as of yesterday my TDS just went to 11.

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the usable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog.

Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons.

Regarding your RO membrane and DI resin, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in three places:
1. Tap water
2. After the RO but before the DI
3. After the DI.

The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down to somewhere near zero?

If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called “prefilters”) do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the “in” port on your RO housing and you'll see it is still approximately 400 ppm.

The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka “permeate”), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependent upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membrane’s advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.

After the RO membrane, water will flow to your DI housing. DI resin in good condition will reduce the 40 ppm water down to 0 or 1 ppm. When the DI output starts creeping up from 0 or 1 ppm, you know that your resin needs to be replaced. Sometimes people complain that their DI resin didn't last very long. Often the culprit is a malfunctioning RO membrane sending the DI resin “dirty” water. This will exhaust the resin quicker than would otherwise have been the case. Sometimes the problem is poor quality resin – remember that all resins are not created equal.


Ray - make sure you sanitize your system, especially after leaving filters in that long.

Russ