Cooling system - tap water OK temporarily?

[LittleSister]

I want to run the engine (indirectly cooled Bukh DV10) in our 'project boat' for about 20 minutes with minimal load (not ideal, I know, but . . . .). The freshwater side of the sytem is currently drained and will need to be drained again after it has been run. When set up for normal use I would anticipate using de-ionised water and antifreeze, but any reason I shouldn't use just tap water (quite hard water round here) for this brief run?

 

[PuffTheMagicDragon]

I don't see any problem.
So your tap water is very hard and you are proposing to run the engine for half-an-hour. Look at it this way: if you were to boil a kettle of that water until it is totally evaporated, how much scale would be left in the kettle?

 

[PaulRainbow]

No problem at all. I can't imagine why you would go to the expense of de-ionised water in an engine. 50/50 tap water and anti-freeze is fine.

 

[David2452]

Probably fine provided it's not going to be standing for some time before introducing the A/F, otherwise I would for the sake of a fiver just add some inhibitor. Buy your A/F premixed and it will be fine as they all use deionised water.

 

[nigelmercier]

50/50 tap water and anti-freeze is fine.

For a start it depends on the concentration, but using tap water is not ideal.

 

[PaulRainbow]

Unless you are changing your water every hour there is no benefit to using de-ionised water. Your water systems only hold a few litres of coolant and half that is antifreeze/inhibitor. The amount of impurities in the small amount of water that only gets changed every two to four years, if that, are tiny.

 

[VicS]

No problem at all. I can't imagine why you would go to the expense of de-ionised water in an engine. 50/50 tap water and anti-freeze is fine.

Using distilled or deionised water for dilution is generally advisable if the local tap water supply is hard or high in TDS but its just as easy to buy the antifreeze ready diluted.

In may of their engine manuals VP suggest the dilution water should conform with ASTM D4985:

ASTM D4985:
Total solid particles ...................................... < 340 ppm
Total hardness: ............................................ < 9.5° dH
Chloride......................................................... < 40 ppm
Sulfate ........................................................... < 100 ppm
pH value........................................................ 5,5–9
Silica (acc. ASTM D859).............................. < 20 mg SiO2/l
Iron (acc. ASTM D1068).............................. < 0.10 ppm
Manganese (acc. ASTM D858)................... < 0.05 ppm
Conductivity (acc. ASTM D1125)................ < 500 µS/cm
Organic content, CODMn (acc. ISO8467).... < 15 mg KMnO4/​

Most people though won't have a clue what the analysis of their tap water is. Even I don't know the analysis of my tap water. My advice would simply be you are in a hard water area dilute the antifreeze with distilled or deionised water or buy it ready diluted.

For the OP's current purpose I'd just use plain tap water .

 

[LittleSister]

Thank you, one and all.:encouragement:

 

[ChrisRayner]

Premixed coolant is available from halfords cheaply. There are two types. One is usually blue, and contains ethylene glycol, the other is pink, and doesn't. Most marine engines use the blue glycol one. If you use water you'll just have to drain and refill, so I'd not do so. Furthermore, coolant boils at a higher temperature than water, which could be bad.

 

[VicS]

Premixed coolant is available from halfords cheaply. There are two types. One is usually blue, and contains ethylene glycol, the other is pink, and doesn't. Most marine engines use the blue glycol one. If you use water you'll just have to drain and refill, so I'd not do so. Furthermore, coolant boils at a higher temperature than water, which could be bad.

No both types are ethylene glycol based. The difference is in the corrosion inhibitors used.

One has low silicate inhibitor and is generally recommended for older engines.

The other, sometimes described as "long life" or "advanced" has an "organic acid technology", or OAT, inhibitor . It is generally used in newer engines

Having said that you will find a non toxic propylene glycol based antifreeze available for such things as RV water systems, but i dont think Halfords sell it

If you look hard enough you may also find propylene glycol based engine antifreeze but I am pretty sure not in Halfords


Surely one of the advantages of an ethylene glycol / water mix is that it boils at a higher temperature than plain water. I dont understand why you consider that to be a bad thing.


EDIT Just checked your profile. You fear an increased risk of scalding presumably.

 

[ChrisRayner]

Thanks for the correction, I expressed myself poorly. The water boiling at a lower temp may result in its boiling off prematurely. Depends on working temperature of the engine

 

[Birdseye]

I want to run the engine (indirectly cooled Bukh DV10) in our 'project boat' for about 20 minutes with minimal load (not ideal, I know, but . . . .). The freshwater side of the sytem is currently drained and will need to be drained again after it has been run. When set up for normal use I would anticipate using de-ionised water and antifreeze, but any reason I shouldn't use just tap water (quite hard water round here) for this brief run?

I'm surprised you would ever bother using anything else. A Bukh is a crude heavy old lump - we arent talking Mercedes F1 engine here. Just get on with it and dont give it a moments thought.