Tuesday, April 24, 2018

DIY Water Leak Alarm with Automatic Water Pump Disconnect Relay

The SHUREflo Accumulator in our Agile developed a small leak, and as usual, I forgot to switch off the water pump and it continued to cycle on and off while we were gone for a hike…luckily, it was a short hike and was immediately greeted by the blaring water leak alarm sound as soon as got into the van.

For the above reason, I decided to build a water leak alarm with automatic water pump disconnect relay. The idea is to disconnect the water pump when sensor senses water; additional wired sensors or maybe wireless sensors can be added later.

Things you need for this project (clicking on the links will take you to Amazon):
·        Rain sensor module with relay control
·        Automotive heavy duty 5-pin 40/30-amp relay
·        16 or 14- gauge wires
·        2-3 feet of smaller gauge wires for the sensor
·        12-volt Piezo Electronic Buzzer Alarm
·        Project enclosure
·        SPST switch
·        Cable gland (optional)

Below is the circuit diagram of the water alarm with water pump disconnect relay. There are many ways to wire this, but this is how I did mine...almost. The water leak module relay is rated 10 amps DC which is probably rated for resistive load on the NO terminal. The built-in relay can probably handle the 7.5 amp water pump inductive load but most likely will not last. Adding a heavy duty 40/30 amp- relay should make it "bullet-proof". The device draws about 0.03 amps and 0.103 amps with the relays energized.


Before tackling on the project, I disassembled the accumulator to check the integrity of the diaphragm; to my surprise it was intact. For the curious ones, picture below is the innards’ of the SHUREflo accumulator. One thing I noticed though is the 7-year old Butyl diaphragm is starting to deteriorate and rubbing off black residue as you can see in the picture; there is also lots of black residue inside the accumulator housing which appears to be from the Butyl rubber. I checked SHUREflo website and no mention if the diaphragm is made of food grade Butyl, but they did mention that it does not have a taste…great. Anyways, it did not concern me as I don’t drink from the tank.

It was a good excuse for me to buy a new water pump and get rid of the accumulator...so I hoped. I looked at the new SHUREflo 4008-101-E65 3.0 Revolution Water Pump with internal bypass which claims low cycling without the use of accumulator tank. The new water pump runs quieter than the stock one. The internal bypass works good almost eliminating pump cycling except when faucet is open to just a trickle, then it starts to cycle. I was able to fix the accumulator at this point (just couple of loose screws caused the leak), so I slapped it back on and that totally eliminates pump cycling. I use the old pump as a spare, an addition to my collection of spare parts stashed on every crevice in the van. :-)

The project enclosure (3.9" x 2.7" x 1.6") that I got is a little small for this project so it looks really cram inside. I painted the clear acrylic cover with black paint and masked 2 small circular clear openings for the LED indicators.

I use a heavy duty DC switch to literally bypass the relay in case the relay fails. For most applications, you don't need a high current switch similar to what I have used, you only need to switch off the water sensor module to bypass the system (see circuit diagram above). The (+) 12-volt DC power and the (+) wire to pump are connected directly to the "normally closed" terminals of the automotive relay so the circuit to the pump is always live.

When "bypass" switch is engaged, the water leak module is powered-off thus de-energizing the automotive relay in a water leak event, doing this restores power to the water pump and also disables the alarm. 

The water leak alarm "red LED" is the power indicator, the "green LED" indicates that it is inactive (no leaks detected). The water sensor is a DIY using 2 strips of stainless steel strip zip ties cut to length then 3M double sided taped into the floor of the van. The water leak relay module that I got did not came with the sensor, it's 3 dollar cheaper than the one I linked above.

 The new SHUREflo 4008-101-E65 3.0 Revolution Water Pump  installed using my DIY vibration isolation mount. You can barely hear the pump running from the galley sink (about 4 feet away).

The freed-up space next to the water pump is now our dirty clothes hamper, it can hold about a week of our dirty clothing.


  1. I’m trying to access my accumulator in my 1999 Roadtrek Popular 190. I have no clue where it is! I replaced the water pump . Can anyone direct me to the access panel of the accumulator?

    1. The accumulator is an aftermarket addition,RT's does not come with it from the factory. If equipped, installers usually connect it next to the pump.


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