If you’re monitoring a shelf of houseplants or several raised beds, this multi-pack of capacitive sensors (about 4.2 stars from 245 ratings) keeps the cost per pot low. An ESP32 has enough ADC1 channels to read several sensors directly; for more, add an I2C ADC such as the ADS1115. Batches of these generic modules can vary, so calibrate each sensor individually rather than sharing one threshold.

For a first project with one plant, this smaller kit (about 4.0 stars from 140 ratings) has a capacitive soil sensor, a 1-channel 5V relay, a mini pump and tubing. Add any ESP32 board and you have a complete, Wi-Fi-connected watering system in an afternoon, a great way to learn ADC reading, relay control and simple automation logic before scaling up.

The tiny 3–5 V pumps in most kits are fine for a few pots but wear out quickly and can’t lift water far. HiLetgo’s 12 V brushless pumps (about 4.1 stars from 504 ratings) move up to 240 L/h with a 3 m head, enough to feed a drip line from a tank or water barrel. Brushless motors last much longer and run quietly. Switch them with a MOSFET module, and protect them with a float switch, because they’re damaged by running dry.

A peristaltic pump squeezes a tube with rollers, so the liquid never touches the motor and every rotation moves a consistent volume. That makes it ideal for hydroponic nutrient dosing, pH adjustment, or watering small pots with exact amounts. This 12 V pump (about 4.5 stars from 316 ratings, the best-rated pump here) is self-priming and can run dry without damage. Calibrate by timing how long it takes to pump a known volume, then water by run time. 16 were in stock when we checked.

For a garden connected to a tap, a solenoid valve replaces the pump: the ESP32 opens it to start watering. HFS’s 12 V, 1/2-inch NPT valve (about 4.4 stars from 993 ratings) is normally closed, so it shuts off if power fails, which is the safe default for irrigation. Two important points: many valves of this size are pilot-operated and need some water pressure to open, so for a gravity-fed rain barrel choose a valve rated for zero pressure or use a pump instead; and a solenoid draws current the whole time it’s open, so size your 12 V supply accordingly and add a flyback diode.

For DC pumps and valves, a MOSFET module is better than a mechanical relay: it’s silent, never wears out, and lets you use PWM to soft-start or slow a pump. These dual-MOSFET modules (about 4.3 stars from 231 ratings) switch 5–36 V at up to 15 A from a logic-level signal, and the 5-pack covers several zones. Connect the ESP32 GPIO and ground to the trigger input, put the module in the negative lead of the load, and fit a flyback diode across each pump or valve to absorb voltage spikes. For mains-powered pumps, use a proper relay board instead; see our relay board guide.

A flow sensor turns “the valve was open for 10 minutes” into “the garden got 40 litres”, and it can detect a stuck valve or burst hose. This 1/2-inch, food-grade Hall sensor (about 4.2 stars from 206 ratings) outputs a pulse train proportional to flow across 1–30 L/min. Count the pulses with the ESP32’s PCNT peripheral or an interrupt and convert using the sensor’s pulses-per-litre factor. If you power it at 5 V, use a voltage divider on the signal line to protect the 3.3 V GPIO. 18 were in stock when we checked.

A float switch in your reservoir is the cheapest insurance in the whole system: it tells the ESP32 when the tank is low, so the pump never runs dry and burns out, and it can send you a “refill the tank” notification. These side-mount floats (about 4.2 stars from 114 ratings) act as simple contacts. Wire one to a GPIO with the internal pull-up enabled and read it like a button. Mount two at different heights for low and high levels.

Kit pumps never come with enough tubing, and different pumps use different outlet sizes. This assortment (about 4.5 stars from 1,599 ratings) includes 2, 3, 4 and 5 mm inner diameters, 12 m in total, so you can match any small pump and run lines to every pot. A useful trick: pierce small holes along a closed-off length of tube to make a simple drip line for a planter.

12 V pumps and solenoid valves need a supply with headroom. This ETL-listed 12 V, 2 A adapter (about 4.5 stars from 3,968 ratings) runs a brushless pump or a solenoid valve comfortably. Feed the ESP32 from the same supply through a buck converter set to 5 V, so the whole system plugs into one outlet; our batteries and power guide covers buck converters and solar options for remote gardens. Keep the adapter indoors or in a weatherproof box.

One houseplant

ESP32 + the 1-channel kit, with a float switch in the water jug.

A shelf of plants

ESP32 + the 4-plant kit + extra tubing + a float switch.

Rain barrel drip line

12V brushless pump + MOSFET module + float switch + 12V supply.

Tap-fed garden zone

Solenoid valve + MOSFET module + flow sensor + soil sensors.

Hydroponics

Peristaltic dosing pumps + MOSFET modules + a level switch.

Why does my soil reading jump around?

Analog readings are noisy, and Wi-Fi activity adds more noise. Average 10 to 20 samples, read only on ADC1 pins, keep sensor wires short or twisted, and add a small capacitor at the ADC input. Use hysteresis (separate “start” and “stop” thresholds) so the pump doesn’t cycle on and off.

Relay or MOSFET for the pump?

For DC pumps and valves, a MOSFET module is silent, lasts forever and supports PWM. Use a relay only for AC loads or where you need full electrical isolation, and use a properly rated board for anything on mains voltage.

How do I stop the system from flooding my house?

Build in limits: a maximum run time per watering, a maximum number of waterings per day, normally closed valves, and a flow sensor or float switch to detect problems. Also make sure the pump turns off if the ESP32 resets or loses Wi-Fi, by setting the output low at boot.

Can I run it on batteries or solar?

Yes for sensing: the ESP32 can wake from deep sleep, read the soil, report and sleep again for months on a battery. Pumps and valves need much more power, so pair a solar panel with a larger battery. See our ESP32 deep sleep tutorial.

Can I connect it to Home Assistant?

Yes. ESPHome supports analog soil sensors, GPIO switches for pumps and valves, pulse counters for flow sensors and binary sensors for float switches, so the whole system can be configured in YAML. Alternatively, publish readings over MQTT with our ESP32 MQTT tutorial.