leak detecting tape?

I notice most leak detectors are single point sensors.  However, under a kitchen sink, over time drips can happen in different areas, so you may not get lucky on just where you put a leak detector.  I'm thinking of maybe laying down two parallel strips of conductive tape at the three (maybe all four) edges of the cabinet bottom under the kitchen sink, and connecting one to ground and one to an external interrupt pin, both on an arduino, so that no matter which way a leak travels, the sleeping arduino will get an interrupt and I'll get early warning.  Just wondering if anyone has already tried that or whether there are any pitfalls to that approach. 
 
I've got reverse osmosis, a waste disposer (which obviously shakes things up every time it runs), and two dishwashers that drain into that space, plus the faucet, its hose connections,  and the sink itself, so there is a lot of potential for something to come loose and drip.  In fact, I just fixed a small drip which I found in the course of repairing one of the dishwashers.  Luckily no damage this time, but Murphy's law is why I'm thinking how I might catch it sooner next time. 

Attempting to detect leaks everywhere is a noble idea, but I'm not sure so realistic.  I'm big into water filters and i have a pretty impressive one that about fills the space under sink.  With pumps and gauges its a leak waiting to happen.  But instead of attempting to detect leaks anywhere, I decided to go a different direction.  First I water proofed the full area with a sealer, then put down a plastic layer, then i built a low tub that everything sits in.  Angle it a bit, and put the leak sensor at the lowest point.  
 
It is really scary how little attention this are gets from the builders, and I bet many people have mold growing down there and they have no clue. 

I used to work on computer systems that were water cooled and we used several different methods for detecting leaks.
 
One was a mat that would go from high resistance to low resistance with just a few drops of water.  It looked like a piece of foam padding about 1/8" thick, and was rather amazing stuff. It didn't matter how large or small the mat was, and you could cut it to size with scissors.  It was made by Warner and they appear to have dropped it, and I haven't found another source for the mats.
 
Here is a similar product, though:  One Drop Alarm
 
There are also water detection "ropes."  These are usually run around the perimeter of a cabinet or a room. 
 
 
This Honeywell RWD41 rope detector is pretty inexpensive and is available at Home Depot. 
 
RLE Technologies also makes sensing cables. You have to combine them with a controller, which is rather pricey (about $200).
 
The One Drop and Honeywell are standalone alarms and would require a bit of hacking if you want to interface them to your alarm system.  The RLE controller has Form C contact outputs.

ano said:

Attempting to detect leaks everywhere is a noble idea, but I'm not sure so realistic.  I'm big into water filters and i have a pretty impressive one that about fills the space under sink.  With pumps and gauges its a leak waiting to happen.  But instead of attempting to detect leaks anywhere, I decided to go a different direction.  First I water proofed the full area with a sealer, then put down a plastic layer, then i built a low tub that everything sits in.  Angle it a bit, and put the leak sensor at the lowest point.  
 
It is really scary how little attention this are gets from the builders, and I bet many people have mold growing down there and they have no clue. 

Click to expand...

Photo?  I'm curious how that looks.
 
Some very expensive high end kitchen cabinets have a custom fitted metal pan in them that are sloped toward the front so as to avoid water damage to the cabinet.
 
My cabinet casework is made out of Melamine laminated to MDF.  I put a thin bead of almost invisible clear silicone around the three edges, and that has (so far) protected me from disaster.  If the MDF were to ever get wet, such as at an edge, it would get totally destroyed. 

GRI water moccasin comes to mind.
 
There's all sorts that are in the data or electrical substation market. The main issue is whether or not the unit is more immune to physical damage, as plenty of them will trip if you look at them wrong or put pressure on them.

The One Drop matt that RAL referenced uses some kind of conductive ink that gets silkscreened on to the matt.  It has what looks like a plastic screen that goes on top to protect the matt.  Now that you've mentioned pressure,  the tank that holds the RO water will be kinda heavy.  I wonder if ithe weight of it would waffle that plastic screen right through the traces of the matt.  However, if it's both resilient and easy to clean, I'd probably get one.  Anyone using one currently?

I siliconed the three sides first. The a basement waterproofer. I think I used Drylok which I had tinted to generally match.  Next a heavyduty plastic shelf liner. then a simple plastic tray with sides about 1" high.  Then all your stuff, and the flood sensor can sit anywhere in the try.  Ideally the flood sensor will turn off the main water valve with something like a Water Cop, but I'm not there quite yet, but its on the list.  Unfortunately these water filters have pressurized tanks, so if the leak is after the tank, shutting off the water doesn't immediately stop the leak, but it should help.

DELInstallations said:

GRI water moccasin comes to mind.
 
There's all sorts that are in the data or electrical substation market. The main issue is whether or not the unit is more immune to physical damage, as plenty of them will trip if you look at them wrong or put pressure on them.

Click to expand...

 
 
The GRI detector looks like a good solution for connecting to an alarm system when a rope detector can be used.  I didn't know they made that one. 
 
Do you have any experience with it in terms of durability, say when used around the perimeter of a cabinet?

I'm noticing this conductive tape also allegedly has conductive adhesive:

http://www.ebay.com/itm/TapeCase-1-2-6-1120-Silver-Aluminum-Foil-Tape-with-Conductive-Acrylic-Adhesive-/111779898643?hash=item1a0699e513
If so, maybe that would make connecting the tape running along the 3 or 4 edges a lot easier.  I think I may have seen similar stuff (?) on windows as part of alarm systems (I assume the theory is that if the window shatters, it cuts the tape and triggers the alarm).
 
Here's the 3M spec sheet:  http://multimedia.3m.com/mws/media/104359O/1120-tape.pdf

From years of dealing with foil on burg systems....three words come to mind. Don't do it. You're asking for problems you don't want to deal with.
 
For the mat, I'd be concerned about false alarms from metallic items (nobody keeps that stuff in cabinets, right?) and weight that could be placed on top of the mylar and surface imperfections. Reminds me too much of the old school floor mats that were installed under carpet.
 
There's plenty of rope type flood detectors out there, the only downside is going to be cost and premade length;usually you're not going to be able to shorten or lengthen in the field. They also typically are not designed for direct connection to a powered alarm loop (alarm panel).
 
The water moccasin is encased in braided nylon, so that helps with physical damage.

Does these rope solutions need to be tacked down at all in order to ensure they lay perfectly flat against the bottom of the cabinet?  Or is it so limp that it just does that naturally?

Come to think of it, it probably wouldn't be that hard to cut a piece of plexiglass or polycarbonate to exactly fit into the bottom of the cabinet, and then glue down some plexiglass edges to it to make a perfectly fitting waterproof bottom   In that case, maybe a single point leak detector would be good enough, and it might look a little nicer than just throwing a generic drip pan under the sink that doesn't exactly fit the cabinet.: 
 

http://www.amazon.com/Under-Sink-Cabinet-Liner-Beige/dp/B00HCGQ86A/ref=sr_1_1?ie=UTF8&qid=1443754680&sr=8-1&keywords=drip+mat+leak+kitchen
 
Maybe someday generating your own custom fitting drip pan like the above would be a good application for a large scale 3D printer, but I  suspect it would  be cost prohibitive to do that currently. 

Finally, I did manage to come across some  leak detecting tape of a different kind::
https://www.dwyer-inst.com/Product/Level/WaterLeakDetectors/ModelWD#ordering
 
though there's little explanation as to how it works.  I suspect it's similar to the rope solutions you all have been discussing, except maybe it uses some kind of tape instead of rope.

I'd be wary because it clearly states that you must physically dry the device after a trip. While a leak detector should never false on their own, we all know how real world scenarios go.
 
The biggest item is going to be the requirement for a sensing head or analyzer between whatever head end you have and the sensor itself. While having a "smart" home with detection for everything you can think of, some items benefit from the KISS principal both for maintenance and operation.

Answering my own question: yes, it appears these ropes do need to be anchored down (at least in Honeywell's case):
 

 
From the sound of the following review, if you can't use the clamps for some reason, it will be tough to get it to lay flat:   http://www.amazon.com/gp/customer-reviews/RDKE37S2H0PV7/ref=cm_cr_pr_rvw_ttl?ie=UTF8&ASIN=B0049U3XE2
 
I would really like the One Drop alarm to work, but when I look at the guy "manufacturing" it, it just doesn't give me confidence as to how long that conductive ink is going to remain stuck to the polyester mat:

 
Given this, I'm going to try a roll of the 3M 1120 aluminum foil tape with conductive acrylic adhesive.  I mean, 3M clearly intends for it to be conductive, so I'm banking on 3M's brand that it should work.  As to durability, I'll put some TBD plastic screen mat over it to hopefully help protect it from abrasion.  As a safeguard, it shouldn't be hard for an arduino to wake up from time to time to "supervise" the foil strip and ensure that it hasn't been accidentally broken or lost conductivity.  In fact, connecting the loop to an interrupt pin is probably all that's needed, or so I hope, unless it picks up so much noise that I need to filter it.