how often do you change sediment filters in RODI

How often do you change your sediment filter (stage 1 I guess) in your RO/DI system?

Before I moved, I was changing it about every 4 weeks - once it turned dark. Now I change it maybe every 5 weeks... I haven't been here but less than 2 months so no real schedule yet.

Anyway, it got me wondering. I'm sure it's dependent on the water in your area, if it's a well, etc. Just wondering what some other reefers are experiencing time wise

 

3 weeks and 5 weeks is way too often. I got my RO/DI filter in July and haven't replaced the filters. I've made about 300 gallons with this unit, and am still getting 5tds out of the RO filter, and 0tds out of the DI. I did replace the DI resin yesterday, but I think it's because the manufacturer's DI resin wasn't the best.

 

Well, after 5 weeks I am still getting low TDS, but all that means is my carbon blocks and membrane are working harder. As sediment filter is so cheap, I change it pretty regularly so I don't have to change the others so often.

In 5 weeks I would guess I've made anywhere between 30 and 250 gallons (not all of that is DI, a lot is just RO for other FW tanks, drinking water, etc.)

 

They recommend every 6 months for sediment filters and every year for RO membrane, depending on usage of course, I think this is for 3000g of usage.

 

I was under the impression that the ESTIMATED change recommendations are roughly 4-6 months on sediment filters and carbon blocks unless a change is necessary sooner due to a 15-20% membrane pressure drop, DI resign is roughly 1 year or when you see a TDS reading above 0, and RO membranes life can vary greatly but life spans upward of 3 years are possible..... Correct me if I am mistaken.

 

I was always told to change the sediment filter when it turned dark. To preserve the rest of the filters in the series. As I have no way to measure between sediment and carbon filters, I go with the color idea. When I first got it, I probably went 6 months then but it was pretty nasty.

It is all estimates as water sources vary considerably. Carbon blocks I have been told 6-9 months depending on use. Since I keep my sediment filter "clean" I go with 9 months on the carbon blocks (or if I see my TDS hover over 20 b4 DI stage).

For me, DI is when TDS is not 0. They generally last me about 18-20 months. I also use color changing resin and find it to be pretty darn accurate. (BRS).

I'm still on my original membrane - making it over 3 years old I believe. I assume I change that when my TDS before DI is out of control (like have to change carbon filters more often than 6 months).

Anyway, feeling like I'm getting descent life out of my filters and my own thoughts are that has to do with the frequent sediment filter changes. basically every time I order something from a place that carries them, I throw in a few to the order; they're pretty cheap compared to the others.

 

Agreed that they vary by your tap water parameters and that they are estimates although I believe pretty close to the truth for most. Glad to hear your over 3 on your membrane that's what i'm hoping for also.

 

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.


Russ

 

12 to 18 months for me in Phoenix with extremely hard water and a TDS of 600 to 1200.

Contact Russ at Buckeye or the folks at Spectrapure and ask about their pleated sediment filters.
I run a 0.2 micron pleated sediment filter that not only filters better but lasts longer due to 10x the surface area and has less pressure or head loss through the filter too so everything performs better.

They are not cheap but they work very well and if you are careful they can be rinsed several times before replacing. I have never had the need to rinse one myself though and at 18 months (WHICH I HIGHLY DISCOURAGE) it still less than a 2 psi drop across the filter. I monitor my filters with two liquid filled pressure gauges, before and after, and use a low range chlorine test kit to monitor for chlorine breakthru on the carbon so can get away with it. Unless you are committed to taking the extra time to monitor stick with the 6 month replacements.

 

Check with Russ at Buckeye or the folks at Spectrapure on one of their pleated sediment filters. It has 10x the surface area of a normal spun poly filter so lasts much longer, filters better since it is lower micron and best of all has lower pressure loss across the filter so the membrane performs better. They can also be rinsed a few times before replacing if you are careful.

Mine is 0.2 microns and lasts over 18 months with less than a 2 psi pressure loss in Phoenix with extremely hard water and a TDS between 600 and 1200. I don't recommend going that long but as a test project I have been doing so by close monitoring with before and after pressure gauges and a low range chlorine test kit to monitor the carbon block condition.
Normally stick to the 6 month schedule since it is easy to remember.