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Purified Water ?


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Hi all. When washing telescope mirrors, it's often recommended

to do a final rinse with distilled water.

However, chemist shops I've asked at, have offered purified water.

Is it ok to use this for the final rinse ?

Thanks for any advise, Ed.

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The three common types of processed "Pure" water that you may be offered are...

1. de-mineralized: std. water softening process utilizing salts and resin beds.

2. de-ionized: processed through de-ionizing resin beds

3. distilled: processed through steam distillation and condensation

Billy...

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I got 1 litre of properly distilled water off eBay back in the summer when I finally thought it was time to clean the mirror. I think it only cost me about £5-6 for two 500ml bottle with postage so not that bad I don't think.

It is only needed for the final rinse to minimize water marks so you don't really use that much, I used one of the bottles when I did my cleaning and there is still quite a bit left (3/4) in the other for when I need it.

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I use 'reverse-osmosis' water which seems fine. It is available from aquarists (tropical fish retailers) and is cheap, cheap, cheap ! (I forget how much but it's roughly 50-70p per gallon, I think)

Spot on, I pay 10p a litre for mine.

Tony..

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Really? I was unaware that Tescos and Halfords did RO, tell me more as I can do without the 30 mile round trip to get mine!

Tony..

It is in the car section, it is in my local Tescos anyway. I have used it in the past as an emergency water supply for carnivorous plants when my water butts ran dry.

Chris

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Yes it is de-ionized water. I have a TDS meter and it is always less than 1 ppm total dissolved solids. Water from my own RO filer and RO filtered water I have bought from aquarium shops have never been that good.

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Interesting. If you're not getting 0 TDS from your own RO unit then it may well need a new part like the membrane or new DI resin. I know where I get my RO from has 0 TDS as it's tested while they're filling up my canisters.

Tony..

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Interesting. If you're not getting 0 TDS from your own RO unit then it may well need a new part like the membrane or new DI resin. I know where I get my RO from has 0 TDS as it's tested while they're filling up my canisters.

Tony..

When my RO filter was new it produced 0 TDS water, but not for long. The tap water here is hard as coffin nails!

Your supplier sounds much better than some of the ones I have tried and have even had to refuse RO water in the past because it had a TDS of over 50 ppm.

Cheers,

Chris

Edited by cgarry
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Blimey, i thought my tap water was hard! It might be worth adding a pre-filter before the RO unit so it might cope a little better.

FWIW, I get my RO from Cambridge Coral Tech in erm, Cambridge. I really should get my own RO unit as it's loads cheaper!

Tony..

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