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Comment by engineer_22 | Hacker News Reader

RO works, but like any solution there are pros and cons

I'm aware it wastes an unfortunate amount of drinkable water. I'm also aware it filters things that might be beneficial, fluoride being one of them. I regret the water usage but I feel it a better alternative to poor health or bottled water, and I use high-fluoride toothpaste to compensate.

Are there other cons I'm not aware of?

energy consumption

My RO system works purely on water pressure and requires no electricity. Do you mean the increased pressure causes increased power consumption?

Water Pressure is a form of potential energy, like rolling a ball up a hill. The RO system is high pressure on the raw side and low pressure on the clean side - the difference in pressure is the consumed energy.

Right that makes sense, but if that’s a serious drain of energy then one would imagine clogged pipes cause dramatically more waste?

Seems like small potatoes compared to having clean drinking water.

Fair point. At utility scale the power requirement is non-trivial. Like anything, there's more than one way to do it, and there's pros and cons to everything. It's up to the owner to decide what they're comfortable with :)

I understand that the difference in pressure at the inlet and outlet of the RO system indicates that work was done moving the water through the system, but the RO system is there to fill a glass of water - it's not clear to me why the outlet pressure is relevant.

Are you saying that the amount of energy it takes to deliver a given volume of water, varies based on the resistance at the outlet?

This poster is in Europe - like most of the rest of the world, they don't have to worry about fluoride removal from water because it's not there in the first place.

Most toothpastes make my teeth sensitive. Interestingly, one of the few that doesn't is fluoride-free. There's been no negative difference in the health of my teeth over the last several years of using that. My experience - fluoride overhyped, especially if you have an electric toothbrush.

You possibly have healthy enamel. I do not - and fluoride has been shown in many studies to prevent tooth decay.

It’s also a heavy metal, so if you don’t have problems with tooth decay I’d say you have nothing to worry about :)

Fluoride isn't a metal!

I'm from Europe and I got several fluoride treatments as a child, with fluoride gel applied for a few minutes. I'm nearly 50 now and I ony had a couple cavities :) So it seems to work. And it's in some toothpastes too. It doesn't have to be in the water.

Counter top ro systems like aqua tru waste very little water, and you get to keep the waste water, eg to water plants

As grumby said, the energy consumption. Power is consumed as the water is forced through the membrane. As the membrane blinded off, more energy is required for the same amount of water.

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