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In a recent reply on the Message Board a member commented that distilled water was NOT the type of water to use in cooling systems because of corrosive properties. He wrote that he preferred tap water.
This puzzled me and after a time, I did some research.
This research suggests that there is an Urban Myth developing about the corrosive properties of distilled water and that it is NOT any more corrosive than is tap water.
It is also better than tap water in that it has none of the mineral contamination existing in tap water.
My internet search revealed the following comments on the matter.
From an article by Gregory T. Fieldson B.S., PhD in Chemistry:
Should I use tap water or distilled water?
I recommend distilled water. If you have exceptionally soft water it would be acceptable, as well. Basically, the engine metals are going to corrode to some extent no matter what water you use, and hard water will encourage the resulting metal salts to precipitate.
From Texaco’s Product Bulletin on DexCool:
However, to maintain the integrity of a cooling system and to help assure long life, deionized or distilled water is preferred over tap water.
These are two (2) of many comments on the use of distilled water in cooling systems.
You can usually buy gallons of distilled water at your local Supermarket for about $1.00 each, so it is pretty cheap.
With most of us only changing out cooling products once per year (we Northerners), it is small change.
Remember to use Win-Cool, NAPA-Cool or whatever similar additive to reduce the corrosive properties of ANY FORM OF WATER that you use.
I trust that you find this information useful, and no, I have no financial ties to the distilled water industry.
Pick and choose the source you want, both sides of the discussion have plenty of published discussions. Urban legend? I guess it depends on if you have awful tap water, then distilled might be better than the swill from the tap.
But the MOST IMPORTANT item is to NOT use distilled water alone, it must be mixed with a corrosion inhibitor, or it will react with the dis-similar metals in the cooling system. Take all the minerals out of the water, and it goes looking for molecules to attach to, facts of physics and molecular characteristics.
I’m blessed with pretty good well water, and it is what I use, with a corrosion inhibitor and in the winter with normal antifreeze: not ‘extended life’ antifreeze, it too attacks old metals and old gaskets and sealants.
Penncool 3000 from Amazon seems to be a good price and fast delivery.
Below copy/paste is from this article: http://www.overclockers.com/pc-water-coolant-chemistry-part-i/
Here are a few real-world examples of the pH values for common water and additive combinations used in PC water-cooling systems. (Beckman F340 pH meter)
*Antifreeze – Prestone (Ethylene Glycol)
**Clorox liquid bleach – 2 Teaspoons bleach (6% Sodium Hypochlorite) in 1 quart water
Notice that distilled water is slightly acidic. This is because distilled water dissolves carbon dioxide from the air forming a weak carbonic acid solution.
Over time, the water in a typical water-cooled PC will slowly become acidic. The pH buffers in water additives (antifreeze, Water Wetter, etc.) will become depleted and periodically need to be replaced. We’ll talk about flushing and refilling later on in the Maintenance section.
Greg Long
It is important to note that one should never use water alone for any prolonged period. You always need something to keep the corrosion down to a minimum.
As far as tap water versus distilled water, you run the risk with tap water of introducing minerals and sediment into the system. This point is clearly made in Greg’s article.
Also stated in the article, which relates to Personal Computer Cooling Systems, the writer in general DOES NOT recommend the use of tap water, but DOES highly recommend the use of distilled water.
Apropos of pH levels, you need to add what you would normally add to any water that you put in you cooling system. Oh yeah, you also need to do periodic maintenance on your cooling system. Distilled water is not toxic to automotive cooling systems and as Greg points out, to each his / her own.
Maybe you warm weather climate guys never flush your systems, but I do it twice per year. When I commission my Series 80 in the spring I drain the antifreeze that sat in the system over the winter to keep it from freezing. I flush the system with tap water and install NAPA Cool with distilled water.
Then in the fall, I drain the NAPA Cool / distilled water solution and replace it with antifreeze. Repeat each spring and fall.
http://www.overclockers.com/pc-water-coolant-chemistry-part-i/
I’ve used 50/50 mix of distilled water only with glycol (usually traditional Prestone) without problem for 30+ years. No corrosion inhibitors and several years between changes. Includes my Packard driven ~1000 miles a year. Only significant corrosion I’ve had is with my nearly all-aluminum Alfa Romeo that’s been my daily driver for 36 years (wet steel cylinders in alum block and head).
My big cooling issues shave been where something in the system – heater core or head- haven’t been thoroughly cleaned out and blocked the upper tubes. 2 out of my 6 cars have Tefba filters because of this, and by the way, I really liked Jack’s super Tefba style filter with magnets. I’ll be doing something similar on my Pierce when I get to that point.
Currently I am lucky in that none of my engines have aluminum head with cast iron block which I don’t doubt would require a lot more frequent changes and corrosion inhibitors due to the large areas of dissimilar metal in the coolant circuit. Spent an interesting weekend a long time ago getting Packard V-12 aluminum cylinder heads unstuck from the block due to corrosion around the studs. I think someone had used nothing but river or dirty well water in it for years, the cylinder jackets were totally packed with sand.
What I like about distilled is that I know what’s not in it.
Jim
Sunday, 26-Apr-2015 at 05:26 PM
Having been an ocean sailor, i had to use a sacrificial ZINC on the stainless steel propeller shaft that had a bronze prop on the end of the shaft.
With that combo, I replaced the zincs every year with no erosion of the very expensive shaft or the more expensive feathering prop.
A few years ago, we discussed this matter on this site and I suggested that the members with aluminum heads on their cast iron blocks to put a zinc in the cylinder head to sacrifice rather than sacrifice the head.
The challenge would be to secure it sufficiently so that it did not dislodge and plug the system.
I am sure that there is a way to effect this modification without causing problems, perhaps in the top of the radiator.
It is an idea anyway as small zincs are available at your local marine shop.
One thing to add if you are using only distiller water with a corrosion inhibitor, pencool, Napa-cool, No-rosion, ect, No-rosion specifically states if you use distiller water with there product you must have a 50/50 mix with antifreeze. If you use tap water you can add it straight to the water. So if you are running distiller water with an additive make sure you read the fine print to see their recommendations.
Here is my original statement regarding distilled water: a copy and paste from my post:
Quote:
If you are running pure water in your car that is a step in the right direction, but If you are using distilled water, I’d add an anti-corrosive agent like PennCool 3000, or similar for an unpressurized cooling system. Distilled water is more ‘active’ in corroding the parts of the cooling system, some form of anti-corrosive should be added.
Unquote.
In this statement I did NOT say that ” distilled water was not the water to use in cooling systems”! I said that IF you are using distilled water I’d add an anti-corrosive agent like PennCool 3000. I DID state that distilled water is more active, since it IS slightly acidic. And I again suggested to use some form of anti-corrosive agent.
Yes, I do use MY tap water, it is very good water, basically what we buy in plastic bottles at stores. My water does not have lots of minerals, and it is changed every year from winter anti-freeze to summer water + corrosion inhibitor. In many decades of using my tap water, I have never had an accumulation of minerals in a radiator or heater core.
While this discussion is a good one for this time of year, for those of us who do change to a mostly water coolant in the spring, I did not miss-state my intended concern about distilled water used alone: If using distilled water, I suggest as well as most others to add an anti corrosive in the cooling system.
Greg Long.