This post first appeared on April 29, 2016.

Milone's eTape is proving to be rather finicky. Per Milone's instructions, I have it installed in a 1" pipe, so that it can't stick to the sides. Readings fluctuate by up to 1/2", even with no change in water level. The eTape seems very sensitive to any sort of pressure. It needs to be suspended to give a proper reading. I neglected to suspend it during one test, and in an empty pipe, readings gradually reached 14", apparently just from the pressure on the bottom of the tape. Worse, according to this discussion, it appears that the eTape can be permanently damaged if it is submerged. That seems to contradict the Operating Instructions, which state:

The vent hole allows the eTape to equilibrate with atmospheric pressure and must not be submerged in the fluid to work properly. The vent hole is fitted with a hydrophobic filter membrane to prevent the eTape from being swamped if inadvertently submerged.

 

I've emailed Milone for clarification.

Update:

According to Chris at Milone, it's ok to submerge the vent hole, but submerging the connector tab will permanently damage the sensor - a detail I'd have thought would be worth mentioning in the Operating Instructions. The newer eTapes that come in tubes are sealed so that this isn't a problem. Chris says that bare eTape can be sealed by using RTV or Silicone II to completely cover the connector tab.

Most mechanical relays and switches are rated for 1 million cycles or less. That sounds like a lot at first, but if you have a sump pump that runs every 30 seconds, that's less than a year. Lowes used to sell a sump pump with a lifetime warranty. Every year, the manufacturer would mail me a new switch, and about every three years, a new pump, until they finally insisted on refunding my money.

Warranties on all the new sump pumps I looked at are awful - most are one to five years, and they expect you to mail the pump in each time. Some don't warranty the switch at all. Not keen on replacing the switch every year, and not wanting the basement to flood, I decided to build a solid-state arduino-controlled system. Water level will be detected using eTape, and the pump will be controlled with a solid-state relay. I've begun putting together a prototype:

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I have a large collection of 18V Porter Cable tools. The oldest are from 2010, and the batteries are starting to fail. I've heard that Harbor Freight's 18V battery uses the same cells. A new Porter Cable battery is about $40, whereas the Harbor Freight battery, with the ubiquitous 20% off coupon, is just $10.40.

Both batteries open by just removing a few screws. The Porter Cable battery is better packaged, but the layout of the cells is identical:

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