homemade water level alarm using a smoke detector

[sdowney717]

http://www.instructables.com/id/Home...r-Hack!/#step1

this looks easy enough anyone could try it.

[willmarsh3]

It looks like it is using the testing function of a smoke detector to also detect rising water by establishing a circuit through the water. For salt water that would almost certainly work. Maybe in fresh water too depending on how much the resistance is. But when the water level is low it would still work fine as a smoke detector as the electronics still work the same.

Thus it would seem to be a good safety device for early detection of flooding as well as fire on a boat.

But a lot of things aren't quite as they appear. Maybe another forumite will come along and explain why this is a bad idea.

[bluedog225]

I wonder how long the wires could be (or what guage they need to be for a long run? I guess you could measure the current and find out.). The alarm needs to be placed above the level of the rising water. Pretty good idea. Would work in utility rooms but only if home. I've been looking at the water cop. Advantage of that is that it shuts the water off.

[hikingchrs]

Seems ok to except that a store bought water alarm is cheaper than a smoke detector.... I think I bought one last spring for $12usd.
Chris

[Lew Barrett]

Or you could hook up a piezo element to the float switch for the cost of the element.

[RichKrough]

I have been using this one for a couple of seasons. I mounted the alarm on the mast partner and fastened the tip of the sensor wire to just above the bilge pump float. I bought mine at Lowes for about $15 plus battery

http://www.basementwatchdog.com/water_alarm.htm

[Bram V]

A Water alarm should be very easy to make, I'll try to Ascii it:
__ |___|
---|= =|----
__ |___|
the | | represents a tube (pvc is what I had in mind) - a wire, and the = is wire with salt crystals. You could also just fill the whole tube with salt water and let that dry up. The tube would fill without resistance, and when the salt dissolves it would make a local salt (conductive) water bridge. Add battery and something that makes noise (and/or a pump), and you are good to go. Do check whether or not the salt is still intact, as well as the battery.

I do confirm that I would use a storebought water alarm myself, but I wished to share my idea.