RO Unit Question

[CoryDude]

Got some pointers from Russ a few years back on something like this. Just monitor the tds output of the membrane, before it enters DI chamber. If you see that start to spike, then your membrane might be nearing the end of it's usefullness. Chlorine destroys a membrane faster than anything, so keep up with your carbon block change-out schedule.

Also, as already said, incoming water pressure makes a huge difference in lifespan and production. We had to get a pressure guage because our house pressure is too high and it damaged a couple of membranes on the ro/unit. Installed a cheapie plastic psi guage from HD (near the water heaters and well pump equipment) for $7. Added it inline right before the water enters the membrane housing. The we ordered a pressure valve from Buckeye. We use it to try and keep the pressure near 80 psi. We get about a 98% rejection rate and 5 gallons of water every 2 hrs.

You'll usually also see better production rates and tds rejections rates during the summer compared to winter months due the the incoming water temp difference.

[alton]

You have to change out the waste water restrictor, it is in your waste water tubing

Is it safe to assume you can switch out a membrane with one that produces more Gpd as long as the fit is the same?

Not going to do that now, seeing I bought this one yesterday.

[BuckeyeHydro]

A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable 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 dependant 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!

Russ

[BuckeyeHydro]

We have a 75 GPD unit from purelyh2o.com and it already had a pressure gauge installed. The recommended psi is 60-80 and we try to keep it at 70psi. It came with a flush kit and I do that once a month.

Sounds like you have a booster pump? If so, you can take better advantage of that and crank your pressure up to 85 to 90 psi.

Russ

[BuckeyeHydro]

I do have another question what is the typical gallons a RO or RO/DI will make in a day if allowed to run. It takes mine forever just to make 5gallons.

Ray - the production from an RODI sytem is determined by the capacity of the membrane, which is expressed in gpd - or gallons per day. Common membrane capacities are 24 gpd, 36 gpd, 50 gpd, 75 gpd, 100 gpd, and 150 gpd.

For any given membrane, it will produce more water with 1) warmer water, and 2) higher pressure. We have a calculator on our website where you can enter your water temperature and pressure and see what your membrane should be producing under those conditions.

The most common cause for production slowing over time is clogged prefilters ("prefilters" are all the filters that treat the water before it gets to the membrane). You'll need a pressure gauge installed after the prefilters to detect this.

Russ

[twychopen]

I got mine from Bulk Reef supply. I got the "fancy" version with the tds monitor b4 and after the di. Also their replacement stuff is as cheap as I have found and very easy to replace. I love it. I highly recommend getting it. Also, I run mine around 40psi and get about 35-40 gallons in 12 hours. I make water once a week and tds reads 00.