RO/DI Questions

[BuffaloReef]

I'm working on setting up a new system and will be replacing my RO membrane and prefilters. I have a bunch of questions so here goes.

I think my RO (reverse osmosis) membrane was rated at 72 gallons per day. Do I have to replace it with the same brand (captive purity) and rating or are they interchangeable? I think a 30 gallon per day membrane would be better for me. I'm going to be using 32 gallon Brute garbage totes so if the pressure and temperature are right it'll take about 24 hours to fill the container. The reason I'm leaning towards a 30 gallon per day membrane is that they're supposed to provide cleaner water since larger output membranes consist of multiple membranes fused together and the membranes may be permiable at the junction.

My unit does not have a DI (deionizer) section. Is the consensus that it's better to use one? I've always felt they remove some trace elements that our livestock may want.

I noticed in another RO thread in this forum that Gary said he does not use a DI stage. In an article I read by Randy Holmes-Farley he mentioned using a DI filter for his makeup water. I also see many local reefers are using them. So there are clearly successful systems running that both use and do not use DI filtration.

I plan to use GFO which removes some of the compounds we want reduced by the DI stage like silica. If the aquarists is using GFO does that make a difference whether or not they use a DI stage?

Finally, as far as DI goes, will I need to have two DI resins, one for anions and one for cations or are DI resins usually built to remove both? I generally see only one DI stage on most systems so I expect they remove both. However, if one filter does remove both types of ions wouldn't its ability to handle the different types be independently depleted causing one users anion filter to be depleted faster than there cation filter and vise-versa for another aquarist?

I may still get a DI stage for emergency purposes since they can get your TDS down to zero with their exclusive use. So, for example if I do need make a large amount of water quickly I can use the pefilters and run them through the DI stage and get lots of clean, but expensive, water in a hurry.

I'd really appreciate feedback on equipment too. What micron/brand would you recommend for pre-filter and carbon block? I'm undecided on brand but am leaning towards .5 micron for both. Would I benefit from adding a second sediment filter, say a 5 micron prefilter before the .5 prefilter? It seems like that could extend the life of the filters. What about the RO membrane brand and DI?

I also need to pick up a TDS meter. I thought this inline TDS meter looked good http://www.marinedepot.com/HM_Digit...Systems-HM_Digital_Inc.-RO1312-FIROPM-vi.html The only thing I don't like about it is that it comes factory calibrated and cannot be calibrated again. I thought I would purchase two of these units giving me four readings. The first would measure incoming water, the second would measure water going from the sediment filter into the carbon block, the third would measure water going into the RO unit and the fourth would measure water after the RO stage. If I do setup a DI stage I would take one of the earlier probes and move it to after the DI. I'm not sure which one but it will probably be before or after the prefilter. I'll also probably pick up a hand-held TDS meter... so much money on TDS meters! Anyway, suggestions on the TDS meters, either a hand-held unit or inline like the one I linked would be appreciated.

Here's an interesting article on "TDS" meters if you're interested. Read it and you'll see why I used quotes http://www.reefkeeping.com/issues/2004-04/rhf/feature/

I noticed when buying some John Guest fittings that there are little metal clips inside them. I don't think the clips would be exposed to water but is that something we should be concerned with? Do we need to by Reef-Safe fittings?

I don't think I would be able to benefit from this idea but since I'm throwing out all these RO questions I'll include it. Would an aquarist be able to boost their pressure with a simple gravity feed setup. I'm thinking something like a municipal water tower on a smaller scale. For example, a 55 gallon drum placed on the floor above the RO stage. The prefilter and carbon block stage would be on the upper floor feeding into the large container and the RO feed tube would run off the bottom of the container, down to the RO membrane.

Thanks for all your help!

 

[cjrbuf1]

What was your question again? Lol

 

[BuffaloReef]

What was your question again? Lol

Yeah, I can get going when I'm curious

My questions can more or less be broken down into:

DI, yes or no and hopefully why?

What media can and should I use with my current equipment?

What TDS meter(s) should I purchase?

 

[SkiFletch]

Many questions here. First off, the membranes are of a standard size and therefore interchangeable. That said, I would stick with 75GPD. It's when you start getting to 100GPD that you loose efficiency and thus higher TDS. The difference in TDS between a 30 and a 75GPD is negligable at best and in the winter, you'll want that 75, trust me.

As for DI resin. I don't use one. I used to, and my DI resin became "spent" and I never bothered to replace it. Didn't notice a single difference in my livestock as a result. I also once re-filled it and still didn't notice any changes. What's 1-2ppm worth of particulate? nothing really. IMHO, DI resin is a waste of time/money/resources which does not warrant it's benefit. Others may disagree with me, but that's my opinion. DI resins do remove anions and cations, only one is necessary if youd do choose to use one.

Your filters will depend a lot on your source water. Are you on City water? If so, I would reccomend 5 or 10 micron pre-filter mesh, 5 micron carbon, and 0.5 micron carbon in that order. Big particulates are a very real issue in the City with old cast-iron pipes everywhere. Even if your house has been upgraded to copper, the mains are all cast iron still for the most part. I would even suggest 4 filters if you can do it. 10m mesh, 5m mesh, 1m carbon, 0.5m carbon. That way your 10 and 5 will burn out relatively quick but they're cheaper as mesh-only. They will scrub most though to save the carbon which are expensive.

TDS meters are TDS meters. They're just resistivity meters so there's really nothing to calibrate. All simple analog solid-state electronics, only the digital displays are fancy . In order to truly calibrate them, you really need to take them out, clean them good, and do all kinds of work that just isn't really necessary for an aquarium based application. What you're looking for are drastic changes in TDS to indicate a spent filter. Here are the take-homes that you need to consider when using TDS meters for most normal RO applications from Randy's article:

7. If you are using a TDS or conductivity meter to monitor the performance of an RO membrane, then the measured value should drop by at least a factor of 10 from the starting tap water. So, for example, if the tap water reads 231 ppm, then the RO water should be less than 23 ppm. In many cases, it will drop much more than that. Less of a drop than a factor of 10 indicates a problem with the RO membrane.

8. If you are using a TDS or conductivity meter to monitor the performance of an RO/DI system, then the measured value should drop to near zero. Maybe 0-1 ppm. Higher values indicate that something is not functioning properly, or that the DI resin is becoming saturated and needs replacement. However, that does not necessarily mean that 2 ppm water is not OK to use. But beware that it may begin to rise fairly sharply when the resin becomes saturated. Do not agonize over 1 ppm vs. zero ppm. While pure water has a TDS well below 1 ppm, uncertainties from carbon dioxide in the air (which gets into the water and ionizes to provide some conductivity) and the TDS meter itself may yield results of 1 or 2 ppm even from pure water.

The metal in john guest fittings is fine. As for your water-tower idea, I'm not sure what you're trying to accomplish. If you want to boost your pressure, you'd need it HIGH, like an actual water tower, to actually make any difference. City water is like 30ish PSI usually which is far shy of "ideal" RO membrane's 60-70 or so that they like. So to make up 30 PSI, you'd need about 70 or so feet of head pressure. That's a lot. Even at 35 feet of head you're only at 15psi. It's like re-inventing the wheel... If you really want increased pressure, booster pumps are the way to go

 

[BuffaloReef]

Thanks for the thoughtful reply Mike!

I'm in the Elmwood Village section of Buffalo so not only is it city water but the plumbing around me is very old! I like your idea of four stages. I read in another RO thread that you do not want the carbon block rating smaller than the sediment filter since then the carbon block will be working, and getting clogged, like a sediment filter. Seems like a good suggestion. Like you.said sediment filters are cheaper than carbon blocks so let them take the abuse.

It's good to see you're having quality results without a DI stage. I expect there will be several opinions on both sides of the issue.

Like I said, I don't think he water tower would work for me. I don't want to give up the room. My understanding is that "rainfall" showers work in a similar manner, so it seems plausible. You might be right about it having to be unworkably tall. I think the depth of the container would have more impact than the height it's kept at. Regardless, I don't think I'll be trying it in this house.

I probably will get a booster pump... another suggestion needed!

 

[cjrbuf1]

Not to hijack the thread, but if I were to remove my DI, would I have to change the placement of the TDS meter. It currently reads "IN" to the DI and then "OUT" from the DI.

Most times the reading is 0-1 ppm going "IN" to the DI filter.

 

[BuffaloReef]

Not to hijack the thread, but if I were to remove my DI, would I have to change the placement of the TDS meter. It currently reads "IN" to the DI and then "OUT" from the DI.

If you're using something like the one I linked I'm pretty sure it just tests TDS. It is supposed to point a certain way as far as flow, but where in the system it is shouldn't matter. The in and out is just to correspond to the readout on the screen.

 

[Buckeye Hydro]

I think my RO (reverse osmosis) membrane was rated at 72 gallons per day. Do I have to replace it with the same brand (captive purity) and rating or are they interchangeable? I think a 30 gallon per day membrane would be better for me. I'm going to be using 32 gallon Brute garbage totes so if the pressure and temperature are right it'll take about 24 hours to fill the container. The reason I'm leaning towards a 30 gallon per day membrane is that they're supposed to provide cleaner water since larger output membranes consist of multiple membranes fused together and the membranes may be permiable at the junction.

As mentioned above, I'd stick with your current 75 gpd membrane.

Because you probably don't have the factory spec pressure and temperature, you're unlikely to get the full 75 gpd out of the membrane. Use the calculator on our homepage to plug in your pressure and temperature and see how much you'll get. Remember that your tap water gets colder in winter.

Membrane 75 gpd and below are speced at 96 to 98% rejection.

My unit does not have a DI (deionizer) section. Is the consensus that it's better to use one?

Yes

I plan to use GFO which removes some of the compounds we want reduced by the DI stage like silica. If the aquarists is using GFO does that make a difference whether or not they use a DI stage?

No

Finally, as far as DI goes, will I need to have two DI resins, one for anions and one for cations or are DI resins usually built to remove both? I generally see only one DI stage on most systems so I expect they remove both. However, if one filter does remove both types of ions wouldn't its ability to handle the different types be independently depleted causing one users anion filter to be depleted faster than there cation filter and vise-versa for another aquarist?

Good question. Most people use a single cartridge of mixed bed resin. Meaning that is a mixture of anion and cation beads. They are mixed in a ratio that provides for an equal capacity to remove anions and cations.

You could run separate beds if you wanted to. You'll get better treatment (lower TDS) from an equal volume of mixed bed resin.

What micron/brand would you recommend for pre-filter and carbon block? I'm undecided on brand but am leaning towards .5 micron for both. Would I benefit from adding a second sediment filter, say a 5 micron prefilter before the .5 prefilter? It seems like that could extend the life of the filters. What about the RO membrane brand and DI?

Concerning what brand - well, we are more than a little biased there so I won't touch that question.
As you are on city water, and assuming you've checked and you don't have chloramines, a good combo is a 1 micron sediment filter and a 0.5 mic, 20,000 gallon carbon block is a good choice. Add more sediment filters or carbon blocks only if you are trying to address some specific water quality issue. We'd be happy to sell everyone multiple sediment filters and carbon blocks, but in most cases they aren't needed.

I also need to pick up a TDS meter.

In general, handhelds are more accurate and some people feel inline meters are more convenient. With an RO system you'd only need one inline meter with two probes. One would measure the feedwater, and one the RO water. The DM2 or DM1 are both very popular. We have a thread in our sponsor's forum describing some new features of the DM2.

I noticed when buying some John Guest fittings that there are little metal clips inside them. I don't think the clips would be exposed to water but is that something we should be concerned with? Do we need to by Reef-Safe fittings?

No

Would an aquarist be able to boost their pressure with a simple gravity feed setup. I'm thinking something like a municipal water tower on a smaller scale. For example, a 55 gallon drum placed on the floor above the RO stage. The prefilter and carbon block stage would be on the upper floor feeding into the large container and the RO feed tube would run off the bottom of the container, down to the RO membrane.

No. To boost the pressure use a booster pump.

Russ

 

[cardiffgiant]

I remember reading that TMZ uses two DI canisters, with his TDS meter measuring what happens between the two of them. The first canister is filtering the water down to 0 TDS and the second canister prevents the TDS from exceeding 0 when the first is spent. As soon as the water coming out of the first canister has a TDS reading over 0 he switches them and replaces the resin in the spent canister.

I'm considering doing the same thing and might pick up an extra DI cartridge during one of BRS's monthly group buys.