Make the SpaSitter  to perform web based monitoring of the water chemistry for swimming pools, hot tubs and other water bodies.  We have spent over a year testing the continued use of the pH and ORP (Oxidation Reduction Potential) probes in a hot tub environment.   They remain very accurate and react great to changes in water quality.

Its easy to use!  Drop the sensors into the water and put the electronics in a water proof project box.  Run a Ethernet line out to the monitor and plug it into a power supply.

  • Temperature monitoring -  A stainless steal encapsulated DS18B20 one wire temperature sensor for water proof temperature readings. 
  • pH / ORP  monitoring -  Determine when your hot tub needs chemicals before it gets green.  After heavy use the ORP level drops dramatically if there is not enough sanitation added to the water. 
  • Email or text message alerts -  Cosm.com has great options and add on features that alert you when your chosen parameter falls outside a selected value. 
  • Smart phone access - Add a Cosm widget to your smart phone and always have access your pool or spa conditions
  • High quality probes -  The kit comes with industrial grade pH and ORP probes.  Ideal for prolonged reading.  High polymer gel-filled design requires virtually no maintenance as there is no need to refill the reference chamber


  1. Could this be extended to control the temperature, automatically, or manually via your phone?

  2. Very Cool .. Im interested in building one.. I love that its a DYI type of device and not a store bought solution..
    I do have a question.. do you know of or have any way to monitor the Hot tub Bromine levels in the case of a salt water spa?
    Ideally, I would look to monitor Temp, PH, Bromine, and ALkalinty levels... any help you can offer would be awesome. thanks