Water indicating crystals

Can anyone think of a powder / crystalline substance I can use to try and prove an intermittent small water leak. I want something that will
positively change colour if wetted, but doesn't change just left in the atmosphere.
I am trying to convince myself that an automatic air vent on an oil fired boiler is the cause of a loss of system pressure by leaking when it shouldn't. I would just change the thing - they are only about 10, but it is in a very inaccessible position so that is not an easy option. However I can sprinkle a powder on it from above!
AWEM
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andrew Mawson wrote:

Most chemicals I can think of that have a clear colour change eg copper sulphate, cobalt chloride etc will eventually change due to atmospheric moisture.
I tend to tie/wire a piece of kitchen towel around the suspect device or newspaper for a large pipe. This will usually stay wet after the leak has self sealed and even if the pipe runs hot enough to dry the tell-tale, it will have changed visually enough to indicate if there is a problem.
hth
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 01/04/2013 16:34, Andrew Mawson wrote:

I wonder if almost any powder will sort of coagulate and form a crust if wetted, sufficiently to see that it had got wet. We feed the wild birds with porridge oats and that cetainly changes its appearance after rain. Worth a test or two with whatever comes to hand.
Henry
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Monday, 1 April 2013 16:34:09 UTC+1, Andrew Mawson wrote:

it

I

You can also try a small bad of silica gel as this changes colour from gold to blue when it absorbs water.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Traditionally, anhydrous cobalt chloride paper is used in chemical tests for water, it changes colour from blue to pink but as someone else has pointed out, over a period of time this will absorb atmospheric moisture unless in a dry place (although it ought to be dry and warm near the boiler which would mean you would have to check it every few hours as the drying effect could reverse the process). If you know a governor or someone who works at your local comprehensive school they should be able to scrounge some from the chemistry department.
I bought a water sensor from Lidl for about 5pounds some years ago which worked quite well. It gave off a loud noise. The following would be similar: (Amazon.com product link shortened) I used it to confirm that there was an intermittent leak from the back of the washing machine. I don't seem to be able to find it now - may have lent it to someone.
Alan
--
snipped-for-privacy@argonet.co.uk
snipped-for-privacy@riscos.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 1 Apr 2013 16:34:09 +0100, "Andrew Mawson"

If you could inject something like Fluorescein dye into the water you could then use a UV lamp to check if/where there are any leaks. Fairly small quantities light up really well in UV.
I once had a retinal examination that involved injecting some of that stuff into my bloodstream...later that day I had a slash in the gents at a local pub - trough-style urinal & there was a UV tube illuminating the place. Completely freaked out the guy that was standing next to me ;-)
Regards, Tony
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Tony Jeffree" wrote in message wrote:

Tony oh Tony ! Only you !!!!!!
AWEM
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I have heard of the Dong With The Luminous Nose, but never a Man With The Luminous P**s.
Cliff Coggin.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 5 Apr 2013 12:02:44 +0100, "Cliff Coggin"

...or even the man with the luminous dong...
Regards, Tony
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 05/04/13 12:06, Tony Jeffree wrote:

Reminds me of a friends mother who went to the likes of an Anne Summers party and they were shown glow in the dark condoms. On the way home it seems they passed the local airport where a plane was being guided in by someone waving those torches with an illuminated wand end and that had them in hysterics after the glowing condom demo.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 1 Apr 2013 16:34:09 +0100, "Andrew Mawson"

Water (as opposed to atmospheric moisture) indicators are used to detect "water" (usually beer or the contents of a toilet) damage to mobile phones. See eBay item 110781703809 for an example of such. They only (and irreversibly) change colour if liquid has been present.. Basically they are a non hygroscopic powder dye on an absorbent substrate. Any Dylon type dye powder in a filter paper wrapper will do much the same although in a damp atmosphere the home made version will discolour in a few weeks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 01/04/13 16:34, Andrew Mawson wrote:

Teabag? Once wet it goes (and stays) brown.
-- Peter F
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.