Water distillers, filters etc

[mr friendly guy]

I was wondering, how does cheap water filtration devices which you simply connect to a tap like these things compare to expensive plug in electrical water distillers? Or how does electric water filters compare to distillers? From my recollection of high school chemistry distillers should theoretically be better since we are in effect evaporating the water and leaving behind minerals etc.

What I am particularly interested is to what elements they remove and how pure the resulting water is. Presumably the expensive distillers are better, but how much better, since the difference in cost is not small.

In case anyone is wondering and thinking that I have become a health nut wanting to drink distilled water, relax guys, its not for me. Its for these plants which I have ordered off Ebay. I figure they would not only look nice in my garden but also helps in my eternal Jihad against the local fly population. Apparently prolonged use of tap water will kill them, so most websites I have perused suggests either rainwater or distilled water.

[Spectre_nz]

Oh. Maybe that's why my fly traps always died when I tried to grow them as a 10 year old.

It comes down to how well you trust the manufacturers claims. Just looking at it it’s a plastic housing and a white filter element. That's not a lot to go on.
Some kind of small pore filter can take out micro-organisms. That's reasonable in a small filter. To get rid of metal ions you need some kind of ion-exchange activity. Water softeners use the same idea. Calcium and magnesium are pretty easy to take out together. Heavy metals are also easy to catch with a good ion exchange set up. But they're usually larger. And they work by swapping one ion for another - you'd be trading calcium, magnesium and heavy metals for sodium and potassium (probably)
They eventually exchange away all their counter-ions, so after a time they'll stop removing ions. Some ion exchange resins have a colour indicator to let you know how much exchange they've got left in them. I can't tell if that slip on filter has a colour indicator, or even if it’s removing ions. Based on the claim it removes heavy metals it must have some kind of ion exchange material, but it doesn't say whether or not it softens water - removing calcium and magnesium, basically. If you don't get the lot, will your plant still be ok?

It's not impossible for it to do what it claims, but the volume of water it will be able to treat before it is exhausted is small, as it is a small filter. If there is no indicator to let you know when it is exhausted, then you'll have no idea when you need to change filters, and your plants might die anyway.
Distillation would remove the minerals more consistently, but you can never get it down to R/O levels in a metal still. Once you get most of the ions out of water, it'll start leaching replacements out of any metal walled vessel the water is sitting in. A new ion exchange filter will do better initially, but will get worse after a while.

Can you collect rain water in a plastic tank outside? Does it rain much in your part of Australia?

[mr friendly guy]

Based on the claim it removes heavy metals it must have some kind of ion exchange material, but it doesn't say whether or not it softens water - removing calcium and magnesium, basically. If you don't get the lot, will your plant still be ok?

Unsure. However I have read that you could get away with just leaving tap water out for a day or so and then watering. I am still trying to figure out how that actually purifies some of the impurities, but assuming it works it does suggest you don't need the whole distillation business.

Can you collect rain water in a plastic tank outside? Does it rain much in your part of Australia?

Not in my state. We are pretty dry and we have a desalination plant plus water restrictions. Oh, and IIRC the guy in charge of planning for future water use while believing that we will have less water in the future is a climate change denier.

I am leaning towards getting a distillation device just to be on the safe side. I figure I only need to distill once or twice a week as most of them gives me 3-4 L and the plants will be small to start off with. It costs around $250-$300 AUD on Ebay, unless I buy a foreign one which requires me to in turn buy a transformer since they use different settings.

[Broomstick]

Unsure. However I have read that you could get away with just leaving tap water out for a day or so and then watering. I am still trying to figure out how that actually purifies some of the impurities, but assuming it works it does suggest you don't need the whole distillation business.

Letting tap water stand out allows any chlorine used in purification to pass out of it into the atmosphere. It's a technique long used by people keeping fish. Chlorine is toxic to many things, it may be Venus flytraps are more sensitive to chlorine than people are.

As for ion-exchange, if I recall, in their native habitat flytraps live in soils that are naturally poor in nitrogen and phosphorus. If the ion exchange resin increases the phosphorus (I have not idea if it does or not) then it might raise it to levels toxic to flytraps. Extend that reasoning to any other water purification system that might add as well as remove things. Likewise, some water softening systems add chemicals that, while they may be harmless to us, may be bad for flytraps.

Based on this reasoning, unless you know exactly what a purification system is doing chemically, and it's effects on the flytraps, you might be better off sticking to distilled water. In my area distilled water is sold all over the place and relatively inexpensive, enough so that if I were raising flytraps I'd probably just buy it a gallon at a time rather than purchase a distillation system, but maybe you're raising more of these than I think you are. Or maybe in your area a distillation system would be cheaper over a reasonable span of time.

[Spectre_nz]

You wouldn't get phosphates out of an ion-exchange for Calcium/Magnesium. They exchange like charges, so One Mg2+ or Ca2+ for two Na+ or K+. Phosphate ions carry a negitive charge.

However, they do use phosphate as a water softener (Like in some detergent powders) as it binds up the calcium and magnesium as phosphate salts and softenes the water that way. You'd still get 'disolved minerals' in your water which wiki says, venus fly traps do not like.

Come to think of it, water quality will vary by region. Letting the water settle to get chlorine out might work for someone who already has very soft water to begin with, but would be no good if your tap water was pretty hard to start out.

Is there an online resource where you can look up your local water quality? If you're opting for filtration you're better off tailoring the filter to you specific water quality. You may well end up needing something just as costly as a small still.

Distillation will clean it up to a reasonable level regardless of how it starts out, assuming you're using the still correctly.

[Zaune]

How much water are you going to need exactly? You don't need anything terribly sophisticated to distill your own.

[Rabid]

If I'm not mistaken, there is no lack of sun rays in Australia, isn't it ? 'Cause, if you're one of these “do it yourself” kind of guy, I have an idea for ya (wild and untested) :

First, you take a parabolic antenna, which you carefully cover with tinfoil on the concave face, in order to make a reflector.
Second, you find a way to heat a tank of tap water (which you'll have painted in black) with the concentrated solar power from the reflector, and then you recover the condensed steam in a second tank, which gives you “free” distilled water.

Here is a quick example.

[Zaune]

If I'm not mistaken, there is no lack of sun rays in Australia, isn't it ? 'Cause, if you're one of these “do it yourself” kind of guy, I have an idea for ya (wild and untested) :

First, you take a parabolic antenna, which you carefully cover with tinfoil on the concave face, in order to make a reflector.
Second, you find a way to heat a tank of tap water (which you'll have painted in black) with the concentrated solar power from the reflector, and then you recover the condensed steam in a second tank, which gives you “free” distilled water.

Here is a quick example.

Possibly a slight overkill unless he's planning on growing a few dozen of them. A kettle hooked up to a sealed bucket with some plastic tubing ought to do if he only needs a few litres a day.

[mr friendly guy]

How much water are you going to need exactly? You don't need anything terribly sophisticated to distill your own.

I estimate only a few litres per week, since the plants are going to start off small. I imagine I would distill all in one shot and store the remainder. I am generally a "press the button and coming back when its ready" kind of guy.

[Spectre_nz]

After a google search on "watering Venus flytraps" I read that they don't like Sodium either.
Which is another strike against all of the common consumer ion-exchange filters.

[Zaune]

I happened to pass a flower shop that had these in stock, and asked about this. The girl behind the counter seemed to think that just boiling water and letting it cool for a while is more than adequate. Is she actually right? I may just buy myself one.

[mr friendly guy]

link

Venus Fly Traps and all other carnivorous plants should only be watered with distilled water, rain water, reverse osmosis water (from an RO system). However regarding tap or well water, if one measures the water with a TDS (total dissolved solids) meter which indicates a TDS measurement of less than 50 ppm (parts per million), it is safe to use for Venus Flytraps and other carnivorous plants. Although higher levels of TDS can be tolerated (up to 100 ppm (parts per million)) or so, in that case the growing medium would need to be flushed occasionally by watering several times over a period of several hours or perhaps a day, and the plants may benefit from repotting (changing the growing medium) once per year or so.

I suppose if we have some device to measure the TDS we could do an experiment and see if boiling water does it enough.

[Broomstick]

I would think that boiling water would actually concentrate the dissolved solids due to evaporation of the water itself.

[Zaune]

I wondered about that myself, actually.

Hmmm... What about the water collected by a mains-powered dehumidifier?

[Broomstick]

That's water condensed from water vapor in the air? That's a sort of distillation, really. The concern would be possible contamination from whatever the water is condensing on, and/or in the water collection bucket, but aside from that it should be very pure water.

[Raxmei]

When I had a dehumidifier I was warned that the water wasn't drinkable. Looking it up later it looks like the problem is some risk of the water picking up contamination from the coils (including heavy metal from solder) and that the tank usually sits stagnant without ever getting properly sterilized. It's possible to make a dehumidifier with food-grade output but most commercial ones aren't intended for it.

[Zaune]

So much for that idea, then; I'm not testing the theory on potted plants that cost almost five pounds each!

[mr friendly guy]

Well I got myself a water distiller and tested it today. There is some odour from it which is most probably the stuff removed from the purification process. I expect my plants to be delivered in 1 -2 weeks (its just that in my particular state it needs some certificate to approve it etc).