there are three bathrooms and one kitchen Light switch (total of 4 switches) that turn on the lights, and also start a Circulation pump for the hot water system. the intent is that the hot water circulates from the end of the "header" and back to the storage tank. one of the switches has failed and when removing from the box, it looks like a 4 way switch with 2 "regular" wires and 2 "thermostat wires". there are relays in the utility that im pretty sure look after the circulation pump regardless of which Light is activated. do i need to open each location to determine which switches are 4 way and which are 3 way ? i took the old switch to Eecol Electric and the replacement switch they offered has the 4 contacts but the gold/black colors do not match ?

  • Do all the involved switches have 4 terminals and is there a "thermostat wire" connected to all of them? a "4 way switch" for controlling lighting from more than just 2 locations (3-way & 4-way) are a very different beast than a double pole switch (which is probably what you have). robartsd's explanation is excellent. Hook this up with the wrong switch and you could blow the relays controlling the pump, possibly starting a fire. + for robartsd's answer. Mar 4, 2021 at 23:13

1 Answer 1


This sounds like it would use a double pole single throw switch. Each side of the switch would be electrically separate, but they physically turn on and off together. The relay probably just turns on the pump when any of the switches are on. If this were some sort of 4 way setup, turning the light on in two rooms would turn off the pump.

You can test that your new switch is a double pole single throw switch with a continuity tester. All four contacts would be isolated from each other when the switch is in the off position. When the switch is in the on position, you'd have two separate pairs of contacts (probably the one pair on either side of the switch) that have been connected, but there would still be electrical isolation between the pairs. If you want to be extra sure that this is correct, take out one of your existing working switches and confirm that it behaves this way as well.

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