RO Water systems

We are getting extremely close to getting back to work after our little incident with a wild fire. The latest, and seemingly last stumbling block is water quality. The town is finding Benzene in the water system, among other, less toxic contaminants. Oemeta has tested our water themselves and have recommended an RO system to get us back up and running, and to up our game long term for coolant quality and life.

So what are your experiences with RO systems? This will be for coolant only, so we really only need maybe 10 gallons per day, but I'm figuring on a 100 gallon holding tank in case we need to recharge an entire sump, and an inline pump to get pressure back up for the Blaser mixer to work right.

It seems like we could get away with a residential system with how little water we use, but I've got to be missing something. I never get to buy the cheaper option and have it work out.

Here's the last thread on this topic.

be aware true RO water is devoid of all mineral and as such is very corrosive.

The RO membrane filters are rated in gallons per day, the one under my sink is 50 gpd that I changed out from the old 25 gpd. I could have got a 100 gpd at the time, a few years ago. Just be sure to hook it up properly so it can backflush itself. That backflush water could be reused if you water is expensive up there.

iwananew10K said:

be aware true RO water is devoid of all mineral and as such is very corrosive.

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And yet....the coolant manufacturers are all doing test's for customers, and proving
major gains in cutting tool life by using it.

One local machine shop was trucking in 8,000 gallons at a time every 3 months,
the 1 year trials showed 30%-50% greater tool life.

If you read the thread linked to in post 2 it was mentioned that first charge of water should be normal tap water. I think the idea behind RO is to keep the mineral content from building and building over time. I doubt it stays very low for long.

DavidScott said:

Here's the last thread on this topic.

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Dammit, I even searched. Thanks David.

We have a whole-house filtration system we're making the R&D parts for (it is a sister company that we house in our walls); they have at least one mature product ready to ship. Filters are customizable to your needs, including many metals or VOCs, etc. Only thing I don't know is whether or not they have gotten the "softening" filters done yet. Drop me a PM if you want, but I do know the things aren't cheap at this point. We are moving to molding but lots of steps in between.

BTW, the reverse osmosis process itself won't remove Benzene. That said, many systems include pre/post filtration for BTEX and/or other VOCs.

Thanks for the offer Rick, but this time around I'm looking for relatively cheap. I see no reason to use anything other than a $200 home setup for this, since it's only for coolant and we might only use 10-15 gallons per day of water. That, plus a larger holding tank with pump should get the job done even if we need to recharge a sump for whatever reason. That's the theory, anyway.

And right, it's the activated charcoal that does the trick on Benzene, according to my reading. And every RO system comes with two charcoal filters, so looks like even the cheapies should do well for us.

I have a system in the kitchen very similar to the one in he link. It uses standard filters in the three larger canisters. very simple and no special filters you have to get from the company selling it.
You don't need the faucet or the tank but if you could not get them to sell filters only then hook them up between you filters and tank for small amounts of on demand water. Just put a small float valve in the tank so pressue builds up against RO unit when tank is full, this should let it auto backflush.
APEC Reverse Osmosis Drinking Water Filter System 5-Stage Under Sink Filtration | eBay
This should come with 2 charcoal filters in it, if benzine is a worry.
Don't get clear filter housings as algae will grow inside them if any light hits them, dont ask how I know that.

We have a huge DI system in our production (life science) lab with a 200 liter main tank and a continuous circulation throughout the system. Anyway, re corrosion the posts above are right that it is corrosive but as soon as you add stuff to it that osmotic pressure reduces pretty fast. We have see corrosion mostly where the DI water was replaced daily with fresh DI water. It's such a weird substance. Brass will turn the water blue as evidently something like copper sulfate comes out. Brass it turns out likes tap water conductivity, not DI but also not sea water. Weird substance that. We once had a terrible corrosion issue with brass screws acting as standoffs on a stainless plate that was acting as a weight for an inlet tube at the bottom of a tank that got emptied and filled every day. It was like bizarre galvanic corrosion with the brass making the stainless dissolve into weird creepy coloured oxides. But we had other stainless tubes sitting in DI water but coated in about .002" of parylene for electrical insulation and they were fine for years and years. Also certain plastic tubes would get the plasticizer sucked out so the tubes became cloudy and brittle, but again, where fresh DI was being used. Turns out polypropylene and NOT polyethylene is the ticket there.

Anyway, here where you are mixing it with coolant and then circulating it in a system which cuts metal, it should be fine. I can say after 19 years in engineering for life science that mixing up your reagents with really good clean water is always a good thing so without knowing anything else I'd heartily recommend it. More generally, everyone can benefit from knocking as much dirt and minerals out of their water, even if not to get to 18 megahom*cm. Even in Vancouver with our low mineral content water we have a couple of extra filters on our waterjet supply lines and it helps keep everything running better.

Been using cheap ~60 dollar ebay/aquarium shop RO system in our cal lab for more than 5 years and works fine for our needs. For sure its not pharmaceutical grade or purest RO available but it would be more than good enough also for machine shop. Our tap water is ~100PPM TDS and the RO unit outputs something like ~1-2PPM TDS water.

Honestly RO is plenty good enough, you don't gain anything in metal cutting to add DI, only if your running wire EDM do you benefit from going better than straight RO. DI resin is costly and gains you little.

RO what you get out quality wise is kinda directly proportional to the restrictor - pressure differential across the membrane and your starting PPM level. If Mattj's numbers are correct, he could change to a lot smaller flow restrictor and make a lot more (as in multiple times more per day) RO water at a lower quality point. If your bellow 30ppm on a TDS tester, theres very little mineral left in said water. Improving - removing the contamination RO filtration alone does which is typically in the 20x pure 'er or better range means you reduce your mineral build up by a factor of 20, if you were having to change coolant previously every 6 months, thats now once a decade hence going better gains you less and less as the coolant even with perfect filtration and zero PPM make up water will never last forever, it will brake down at some point

I would really not be too worried about trace amounts of benzene in coolant water either, it will largely evaporate off and kinda doubt theres going to be enough present to cause you any issues if your not drinking it. That said, you need carbon filtration pre RO as city waters chlorine will damage - significantly shorten RO membrane life span. If your running on well water then skipping the carbon filtration has little real impact for coolant type use unless your consuming it.

The first batch with straight tap water is some times a good idea, other wise you can get foaming issues, hard water simply pops the bubbles, puer soft water makes longer lasting bubbles.

What percentage of water is dumped down the drain with RO. 25 years ago for home use it was like 5x dumped for 1 volume of RO. Not sure but I bet California has some rules on what you can do with that discharge water.
Bil lD.

Bill D said:

What percentage of water is dumped down the drain with RO. 25 years ago for home use it was like 5x dumped for 1 volume of RO. Not sure but I bet California has some rules on what you can do with that discharge water.
Bil lD.

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As stated in an earlier post, run it to landscape or some other need, it is not like brine backwash from a softener. Size of water bill will help make this decision.

Bill D said:

What percentage of water is dumped down the drain with RO. 25 years ago for home use it was like 5x dumped for 1 volume of RO. Not sure but I bet California has some rules on what you can do with that discharge water.
Bil lD.

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Can be what ever you wish it too, trade off is generally how pure your water is an how pure you want your RO to be. 3-5x1 is a common ball park, but you can go lower than 3:1 if your starting waters not too bad and your not after a very pure output coupled with the type of membrane and just what contaminants are in said water. For the OP's use being pretty non demanding purity wise, theres little point running lots to waste unless his incoming is terrible.

Let me ask the obvious question: if the contaminant of concern is benzene, and if it is filtered out, not by RO, but by the charcoal pre/post filter ... why do you need the RO component at all? The obvious answer may be, because the town said so ... but it sounds like this was a recommendation, not a requirement. What about just using a cheap "whole house filter" with sediment filter + charcoal?

Why does this shit fly right over my head. I read and read and read, and it just doesn't sink in. I seem to have a learning block on this subject.
Anyways, I installed an RO system for coolant. I was having rust issues. Cleaned everything (all the rust) up at that time.
And, I haven't seen any rust since.

I was told the system would dump a 50/50 ratio (it is watering some bushes in the back yard).
I went with a 50gal bladder tank, no pump, and it takes about 5-6 hrs to fill the tank from empty. That friggen tank was $$$.

wheelieking71 said:

I went with a 50gal bladder tank, no pump, and it takes about 5-6 hrs to fill the tank from empty. That friggen tank was $$$.

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Its why most of us cheap skates just have it dump into a container, once its been left on over night and caused a mini flood a couple of times even the cheapest of us cheapskates setup a float switch to turn it off!