DIY RODI

[WillpoleReefers]

I have just got my DIY RODI setup into basic working configuration. It will be developed further, the solenoid valves will be used to allow control of startup using an automated PIC micro based system that will also monitor conductivity at 4 sample sites. At the moment it’s all manually controlled and I have been looking at real world flow rates through the system by timing collection in a measure. For some reason it seemed like a good idea at the time to use a 400gpd membrane and optimise the system around that. Might have been overkill . My current understanding is that the higher flow membranes give a worse rejection ratio, I don’t yet have conductivity measurements to assess this. Raw water is pretty hard in this area with reasonably good mains pressure. Just wondered what the experts here think about using the setup for now in its basic configuration, underutilising the RO membrane. I fitted an adjustable regulator to allow waste water flow to be tuned. Obviously if you turn that flow up inlet pressure does drop a little. Max inlet pressure with inadequate waste flow was about 43psi, at the low end of acceptable. Tuning the waste flow allowed me to set up a 4:1 waste product ratio, real world product flow is about 120 UK gpd and inlet pressure is now 40 psi which I appreciate is lower end. Product water quality appears good based on kit water quality testing, no TDS as yet. My question is whether the system as configured will burn though DI resin. I think whatever I may need to add a much larger resin stage than the current two 10 inch housings. No problem to do this really. The inlet pressure can be increased by adding a booster pump, maybe such membranes really require one of those? Interested in peoples thoughts on this, TIA

Steve

 

[KStatefan]

What are the specs of the membrane you used?
That will depend on what you TDS going into the DI is.
Why is there a carbon block after the membrane?

Edited to add a couple more questions

The flow rate from a 400gpd membrane at 4:1 would cause some concerns for me.
400GPD at 4:1 would be 2000GPD 1.4gpm thru your prefilters. That is much higher then the rating on the carbon filter I use so you would want to check on that also.

 

[Woodyman]

A membrane that size you are going to want a booster.

 

[Woodyman]

What are the specs of the membrane you used?
That will depend on what you TDS going into the DI is.
Why is there a carbon block after the membrane?

I'll wait for you to answer these, but I'm also curious about your sediment pore size choices.

Any reason you did a 20 and then 5? Do you have a large % of larger pieces. Typically you can start with a 5 and step down even lower to a 1 or sub 1 to get a good polish before carbon blocks and prevent clogging them.

 

[WillpoleReefers]

What are the specs of the membrane you used?
That will depend on what you TDS going into the DI is.
Why is there a carbon block after the membrane?

It’s an FCS US made membrane, not sure on the exact specs, pic below. Will need to measure raw water TDS asap for sure. I though having a post membrane carbon block was useful to catch any unfiltered organics?

Steve

 

[WillpoleReefers]

I'll wait for you to answer these, but I'm also curious about your sediment pore size choices.

Any reason you did a 20 and then 5? Do you have a large % of larger pieces. Typically you can start with a 5 and step down even lower to a 1 or sub 1 to get a good polish before carbon blocks and prevent clogging them.

I wasn’t too sure regarding these choices. Info suggested 5u was a good size, I also know that filtration is not 100 pc with one stage, so I added a 20 in front as a prefilter. All is configurable of course if people think 1u is of real world benefit?

Steve

 

[WillpoleReefers]

A membrane that size you are going to want a booster.

Yea I thought it might be necessary, was curious to run it without initially and see what was possible though. It’s not a big issue to add a pump if needed,

Steve

 

[Woodyman]

I wasn’t too sure regarding these choices. Info suggested 5u was a good size, I also know that filtration is not 100 pc with one stage, so I added a 20 in front as a prefilter. All is configurable of course if people think 1u is of real world benefit?

Steve

Do you know the pore size of your carbon? It's generally preferred to run sediment lower to prevent ang clogging in the carbon..

 

[Woodyman]

Here's a read for you that explains that in more detail..

RO/DI Basic Guide

There are always a lot of questions regarding which RO/DI setup do I need, how many stages, how do I know when to change filters/membranes, I’m getting a weird TDS value, etc. Hopefully this clarifies a few things and helps some of you out one day. My first recommendation would be to find the...

www.reef2reef.com

 

[WillpoleReefers]

Here's a read for you that explains that in more detail..

RO/DI Basic Guide

There are always a lot of questions regarding which RO/DI setup do I need, how many stages, how do I know when to change filters/membranes, I’m getting a weird TDS value, etc. Hopefully this clarifies a few things and helps some of you out one day. My first recommendation would be to find the...

www.reef2reef.com

Really useful, just read this thanks!

 

[WillpoleReefers]

Do you know the pore size of your carbon? It's generally preferred to run sediment lower to prevent ang clogging in the carbon..

The carbon blocks are 5 micron, matching the prefilter

 

[Woodyman]

The carbon blocks are 5 micron, matching the prefilter

That's good. Just remember unless you filters rated as absolute they will not effectively filter everything to the 5 micron size.

I'm currently using a 0.35 micron sediment followed by a 1um chloramine carbon block and a 0.5um carbon block.

 

[Woodyman]

Also with a 400gpd membrane I'd just upgrade to 20" housings for the volume your going to be putting through the unit.

As @KStatefan noted do you plan to remove that carbon after the membrane? And do you know the flow ratings on your current pre filters?

 

[WillpoleReefers]

That's good. Just remember unless you filters rated as absolute they will not effectively filter everything to the 5 micron size.

I'm currently using a 0.35 micron sediment followed by a 1um chloramine carbon block and a 0.5um carbon block.

It’s really interesting/useful to learn about the nuances of these choices. The nice thing about a DIY unit is that it is pretty configurable, I didn’t necessarily expect it to be perfect in the first incarnation. I’m thinking that 5 micron prefiltration and carbon just means I get a bit less life out of the membrane. Obviously I can change prefilter size in the future. With hindsight I might have been better with a 300gpd membrane, might look at that when it does start to clog. I can easily set the waste to product ratio for membrane changes with this setup, I’m thinking the adjustable valve will be useful

Steve

 

[WillpoleReefers]

Also with a 400gpd membrane I'd just upgrade to 20" housings for the volume your going to be putting through the unit.

As @KStatefan noted do you plan to remove that carbon after the membrane? And do you know the flow ratings on your current pre filters?

I admit I have no clue as to the flow ratings. I suppose the 10 inch housings may be throttling things a bit. To remove the post carbon in the system as built means going to just one carbon filter, or losing one of the two pre filters. Decisions I guess

Steve

 

[Woodyman]

I admit I have no clue as to the flow ratings. I suppose the 10 inch housings may be throttling things a bit. To remove the post carbon in the system as built means going to just one carbon filter, or losing one of the two pre filters. Decisions I guess

Steve

I would keep both carbons, but I would move it prior to the RO membrane not after. I'd also say drop down the sediment from 5 to 1, and ditch the 20 or replace it with a 5.

 

[WillpoleReefers]

I would keep both carbons, but I would move it prior to the RO membrane not after. I'd also say drop down the sediment from 5 to 1, and ditch the 20 or replace it with a 5.

Cheers. Ratio is 4:1 so not quite so high. I think that’s the direction in which the design is headed, thanks

Steve

 

[KStatefan]

I admit I have no clue as to the flow ratings. I suppose the 10 inch housings may be throttling things a bit. To remove the post carbon in the system as built means going to just one carbon filter, or losing one of the two pre filters. Decisions I guess

Steve

It is not just the pressure drop across the filter it is the contact time the carbon has to remove the chlorine. When you are flowing more the carbon is not removing as much.

 

[Woodyman]

It is not just the pressure drop across the filter it is the contact time the carbon has to remove the chlorine. When you are flowing more the carbon is not removing as much.

Another reason for you to move that second carbon to re membrane and not have it post. There really is no benefit to the DI to have carbon post RO.

 

[WillpoleReefers]

It is not just the pressure drop across the filter it is the contact time the carbon has to remove the chlorine. When you are flowing more the carbon is not removing as much.

Thanks that’s useful data, hence the argument for two carbons before the membrane ideally. Think we may re plumb in that direction. I’m also not going to go anywhere near 400gpd in terms of flow rates

Steve