Ro/di issues

Llorgon · Dec 23, 2019

Alright, my secret santa sent me a TDS meter so I have been testing my water quality and it has raised some issues.

I'm new to making ro/di water. Didn't need it before I moved. So I have a reef crest 4 stage ro/di unit. Bought new and setup middle of October. I usually make about 10 gallons of water a week. Except for a move where I made 30 gallons. So I would say low use.

Now the problem is I already seem to have higher than wanted TDS coming out of my unit. My TDS readings are:
Tap: 146ppm
Ato reservoir(5 gallon aquarium, no lid): 62ppm
Ro/di container: 17ppm
Water from ro/di: 9ppm

Do I need to replace my filters already? I'm assuming the other two high readings are from dust/dirty container?

Some pictures to see what I have.

Johnd651 · Dec 23, 2019

Have you flushed the membrane?

dadnjesse · Dec 23, 2019

Your DI resin looks exhausted.

redfishbluefish · Dec 23, 2019

For starters, what is your source water.....well or city water? The reason I ask is that many aquifers (well water) are high in carbon dioxide, which will eat through DI resin real quick. If this is the case, there are fixes for this.

Second issue, if I can make out that gauge, is that your pressure is too low (looks like 40 psi). Need to get a booster pump to up the pressure. This will help with increasing the efficiency of the membrane.

A quality membrane will lower TDS by at least 98%. Not sure of the brand of membrane in your unit.

Now I would do one more thing....put is a three way valve between the membrane and the DI resin. What you want to do is run the first five minutes or so of start up to waste. The reason is that on start up, you get break through TDS which will also chew up DI resin quickly.

As far as current setup, you definitely need to change out the DI resin.

Llorgon · Dec 23, 2019

Johnd651 said:
Have you flushed the membrane?

I believe I did a flush when I first set it up. I just followed the instructions that came with the unit, but since then I just turn the valve to let the water go through it.

dadnjesse said:
Your DI resin looks exhausted.

New one will be ordered!

redfishbluefish said:
For starters, what is your source water.....well or city water? The reason I ask is that many aquifers (well water) are high in carbon dioxide, which will eat through DI resin real quick. If this is the case, there are fixes for this.

Second issue, if I can make out that gauge, is that your pressure is too low (looks like 40 psi). Need to get a booster pump to up the pressure. This will help with increasing the efficiency of the membrane.

A quality membrane will lower TDS by at least 98%. Not sure of the brand of membrane in your unit.

Now I would do one more thing....put is a three way valve between the membrane and the DI resin. What you want to do is run the first five minutes or so of start up to waste. The reason is that on start up, you get break through TDS which will also chew up DI resin quickly.

As far as current setup, you definitely need to change out the DI resin.

The water source is city at least as far as I know and I have it connected to the cold water line under the sink. I can turn the valve on or off to let the water go through it.

yes water pressure is at 40psi. What pressure should I be aiming for?

I'm not sure of the brand name either. It came with the unit.

Ok I will look for that three way valve.

Llorgon · Jan 28, 2020

So I have finally got the booster pump and have it all setup.

My pressure through the unit is now at about 83psi.

Water from tap 155tds
water out of ro/di unit 4tds

How can I get it down to 0 or is 4 as good as I'm going to get?

Devisissy · Jan 28, 2020

I have a Spectrapure unit and it has inline TDS meters to each stage of the unit which takes all the guessing out of which one of my stages is exhausted. I suggest some inlines to sort of see where the issue is. I think they are relatively cheap and easy to install.

dadnjesse · Jan 28, 2020

You really need to add more stages to get the best filtration.

Llorgon · Jan 30, 2020

Devisissy said:
I have a Spectrapure unit and it has inline TDS meters to each stage of the unit which takes all the guessing out of which one of my stages is exhausted. I suggest some inlines to sort of see where the issue is. I think they are relatively cheap and easy to install.

Alright I will add a inline and see what the tds reads at.

Opus · Jan 30, 2020

You don't really need an inline, they are just for convenience. Plus they don't compensate for temperature when reading tds. Also more stages really doesn't mean better filtration. Depends on what is in your water.

First, see if you can get a copy of your city's water quality report. Here in the US cities are required to issue a report each year and they usually have the latest one posted on their website. Not sure how that works in Canada. This will give us an idea of what is in your water. If you can't find a report, at least try calling them and see if they use chlorine or chloramines in the water. This will dictate what kind of pre-filter you will need to use. If chlorine reaches the RO membrane it will destroy it, chloramines will not but they will eat thru your DI.

Second, can you get us a reading of your tds after the ro membrane but before the di. This will tell us how well the membrane is working.

Also, here is a link to a nice little write-up reef-junky did a week or 2 ago explaining RO units and how they work.

The Basics of an RODI Filter

An RO membrane forces molecules through a semipermeable membrane (certain substances can pass through but not others) to form a less concentrated solution then you started with. The inside of the membrane looks like so: Some of the things an RO membrane can filter out are: Lead Copper...

www.reef2reef.com

Devisissy · Jan 30, 2020

Opus said:
You don't really need an inline, they are just for convenience. Plus they don't compensate for temperature when reading tds. Also more stages really doesn't mean better filtration. Depends on what is in your water.

The Basics of an RODI Filter

An RO membrane forces molecules through a semipermeable membrane (certain substances can pass through but not others) to form a less concentrated solution then you started with. The inside of the membrane looks like so: Some of the things an RO membrane can filter out are: Lead Copper...

www.reef2reef.com

When you have five stages and three of those stages are over $30 to replace. Yes you need the inlines. I do admit I bought the best RO/DI on the market and it is OVERKILL in every single way. But next to my Tunze ATO its been running flawlessly without issue for 7 years. If I didn't have those inlines I would not have any idea when those resins are exhausted or which one. TDS is weight so temp usually in our case doesn't play much of a roll in the actual reading. In a lab setting this would be important. I highly recommend anyone new or thinking of getting into the hobby, buy the BEST RO/DI they can within budget and not mess with after market amazon garbage. Buy the unit first, it should be the first thing you buy.

Opus · Jan 30, 2020

Mine has been working great for 25 years and I have a hand held. Soooooooo

Llorgon · Jan 30, 2020

Opus said:
You don't really need an inline, they are just for convenience. Plus they don't compensate for temperature when reading tds. Also more stages really doesn't mean better filtration. Depends on what is in your water.

First, see if you can get a copy of your city's water quality report. Here in the US cities are required to issue a report each year and they usually have the latest one posted on their website. Not sure how that works in Canada. This will give us an idea of what is in your water. If you can't find a report, at least try calling them and see if they use chlorine or chloramines in the water. This will dictate what kind of pre-filter you will need to use. If chlorine reaches the RO membrane it will destroy it, chloramines will not but they will eat thru your DI.

Second, can you get us a reading of your tds after the ro membrane but before the di. This will tell us how well the membrane is working.

Also, here is a link to a nice little write-up reef-junky did a week or 2 ago explaining RO units and how they work.

The Basics of an RODI Filter

An RO membrane forces molecules through a semipermeable membrane (certain substances can pass through but not others) to form a less concentrated solution then you started with. The inside of the membrane looks like so: Some of the things an RO membrane can filter out are: Lead Copper...

www.reef2reef.com

I will see if I can get a reading after the ro membrane later today or tonight.

For water quality, haven't found much on the city website. I know they use chlorine and the water is very hard. All the water comes from the local lakes so quality isn't great.

Opus · Jan 30, 2020

Llorgon said:
I will see if I can get a reading after the ro membrane later today or tonight.

For water quality, haven't found much on the city website. I know they use chlorine and the water is very hard. All the water comes from the local lakes so quality isn't great.

Why do you say the quality is bad? My water comes from a local lake and my tds is 450. My spectrapure membrane gets that down to 4 tds before the di filter.

Llorgon · Jan 30, 2020

ok today from the tap the tds was 137ppm
From ro before the di 43ppm

We end up with lots of boil water advisories during the year. Fairly common thing. The city says they are working on water quality.

Greg P · Jan 30, 2020

Sample your Waste Water to ensure the unit is plumbed correctly and you're not pumping Waste Water through the RO Membrane and Product Water down the drain.

If the numbers tell you it's plumbed correctly, next release the system pressure and take the Membrane housing apart.
Remove the Membrane and inspect the o-rings for damage. You want to ensure Waste Water is not bypassing the Membrane.
Re-install the Membrane and push it down hard into the housing to ensure it's properly seated, then re-install the cap.
Re-start the unit WITHOUT the DI and flush the system for 15 mins or so. Hopefully you have a flush valve on the unit.
After flushing, run the unit for 5 mins or so, then take a TDS reading - remember this is without the DI included.

With your source water of 137, and a 98% rejection rate, you should be getting close to less than 3 TDS from the Membrane.

Post your results after testing

Greg P · Jan 30, 2020

If you truly are getting high tds from the waste water line, and a somewhat reduced but not low tds from the product line, then there's a good chance the membrane is bypassing somewhat.

Greg P · Jan 30, 2020

There's also a chance the previously low water pressure caused the membrane to fail, possibly due to scaling.
Now that you have proper pressure, going forward it's important to flush the system before each run of product water to help keep the membrane surface from fouling, and to remove tds creep that would otherwise end up in your storage container.

Let us know what your tests show