Testing for saltwater

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Billows

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Any nice hack to check if bilge water is seawater or rainwater other than tasting (yuk and often inconclusive).
 
Apart from precipitating it with Silver Nitrate (AgNO3), try boiling it in a shallow metal dish. If you see salt crystals....

Sea water aquarium keepers have small testing devices, too.
 
I also want to see if a leak is from the sea or the rain. I've licked it, but it doesn’t really tell if it's a mix of rain and sea water. I'm guessing that a hydrometer would work. but I don't know how sensitive and can't remember how to do the calculations. I'll try my battery hydrometer - suck in some sea water to see what 100% local sea water reads, then test the bilge water.
 
dutyhog said:
I'm guessing that a hydrometer would work. but I don't know how sensitive and can't remember how to do the calculations. I'll try my battery hydrometer - suck in some sea water to see what 100% local sea water reads, then test the bilge water.
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Doubt a battery hydrometer would give a useful reading since its range is too high. An (ethylene glycol) antifreeze hydrometer might do the job...or might not. Cheap as chips on-line: https://www.amazon.co.uk/Silverline-427656-Anti-Freeze-Tester-Celsius/dp/B000NBVMTE
(There are such things as salinometers, but probably not at that price.)

Edit: although this isn't too dear: https://www.amazon.co.uk/HZY-Salinity-Household-Salinometer-Electronic/dp/B01IT7HPLW

Anyone with a watermaker could no doubt use their hand-held dissolved solids tester.
 
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The problem is a bilge is likely to have had sea water in it at some time unless it's a sparkly clean AWB so any test is likely to indicate some presence of sea water.
 
petehb said:
The problem is a bilge is likely to have had sea water in it at some time unless it's a sparkly clean AWB so any test is likely to indicate some presence of sea water.
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An SG test would indicate the degree of salinity (assuming there weren't more exotic solutes present, which is improbable). This can be compared with the stuff you're floating on.
 
Presumably your multimeter would give a good clue? The conductivity of sea water is 100-1000x that of potable water. So if you can fix the distance between the terminals and measure the resistance of both as well as your bilge sample it should be clear.
 
petehb said:
And if it's a mixture?
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A mixture of what? If you're thinking of significant quantities of a solute in addition to those in seawater, perhaps you could suggest what it might be. Barring something like a major kitchen accident (which I think even the most cack-handed cook might notice) I'm struggling to imagine a credible compound.
 
Possibly one of these? http://www.ebay.co.uk/itm/Rugged-Hy...064369&hash=item51d599869c:g:V5AAAOSwdGFYwhKr

Test some seawater and note the reading. Test the bilge water and you should be able to estimate the seawater/freshwater mix. On my boat everytime I remove the log some seawater gets in resulting in salt crystals once any I fail to mop up have evaporated, so before measuring any future water leakage I think I may have to wash the bilge with fresh and pump everything out to avoid false readings.
 
macd said:
A mixture of what? If you're thinking of significant quantities of a solute in addition to those in seawater, perhaps you could suggest what it might be. Barring something like a major kitchen accident (which I think even the most cack-handed cook might notice) I'm struggling to imagine a credible compound.
Click to expand...

Norman_E said:
Possibly one of these? http://www.ebay.co.uk/itm/Rugged-Hy...064369&hash=item51d599869c:g:V5AAAOSwdGFYwhKr

Test some seawater and note the reading. Test the bilge water and you should be able to estimate the seawater/freshwater mix. On my boat everytime I remove the log some seawater gets in resulting in salt crystals once any I fail to mop up have evaporated, so before measuring any future water leakage I think I may have to wash the bilge with fresh and pump everything out to avoid false readings.
Click to expand...

Normans post explains what I was indicating, if your result shows a mix of sea and fresh water, quite likely if as there usually will have been some sea water in there at some point you are non the wiser.
 
petehb said:
The problem is a bilge is likely to have had sea water in it at some time unless it's a sparkly clean AWB so any test is likely to indicate some presence of sea water.
Click to expand...

This is true.
Along with various household detergents, spilt tea, and all sorts.

The bilge water in my mate's boat was saltier than the sea!
Basically salt water gets in there on on oilies, spinnakers etc while racing, then the dehumidifier removes a lot of the water.
One could start by giving the bilge a good clean with plenty of fresh water.
Then see what the new bilge water is like.

Tracking down rain leaks keeps you busy!
 
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