resistive water level sensor
http://www.hotmcu.com/water-level-sensor-liquid-water-droplet-depth-detection-p-113.html

Pressure
https://www.quora.com/How-much-would-normal-climate-temperature-variation-affect-pressure-inside-a-pvc-tube-with-a-pressure-sensor

Diaphragm
https://www.alibaba.com/product-detail/Holykell-0-200m-H2O-SS316L-Diaphragm_1514356495.html


Contactless to water.
Analog output
Simple to install
No maintainence
No degrade over time
Simple water tank design
Non Electric Contact
Suitable for all types of liquid
Long diatance


Keywords
water level sensor 
water level sensor singapore
automatic water level controller sensor
overhead tank water level sensor
*rain water level sensor 
water tank level sensor
pond water level sensor
aquarium water level sensor
electrode water level sensor
water level measurement using pressure sensor

contactless water level sensor 
water level sensor types
sensor to detect water level

pressure sensor water level 
river water level sensor
capacitive water level sensor
wifi water tank level sensor 
wireless water level sensor 
*ultrasonic sensor water level
*water level sensor float switch

analog water level sensor 
water level alarm sensor
laser water level sensor



Radar Water Level Sensor (ICENTA)
http://www.icenta.co.uk/level/radar-level-transmitters/

Resistive (THAOYU Electronics)
http://www.hotmcu.com/water-level-sensor-liquid-water-droplet-depth-detection-p-113.html

Capacitive E2K-L (Omron)
https://www.ia.omron.com/products/family/475/specification.html
https://www.ia.omron.com/products/applications/case/53.html

Contactless-Water-Level-Switch-Inductive-Liquid-Level (Banggood)
http://www.banggood.com/Contactless-Water-Level-Switch-Inductive-Liquid-Level-Switch-Water-Level-Sensor-p-1103869.html

Continuous Output Water Level Sensor (FPI Sensors)
https://fpisensors.com/product/continuous-output-level-sensor/

Single Level Water Level Sensor (consoletronix)
http://consoletronix.com/Stainless-Water-Level-Liquid-Sensor-Float-Switch

Cynergy3 Components Ltd
http://www.cynergy3.com/product/12-bsp-external-mount-float-switch
http://www.cynergy3.com/products/product-type/float-switch
http://www.cynergy3.com/blog/how-select-correct-float-switch
http://www.cynergy3.com/product/12-bsp-internal-fitting-float-switch

diaphragm gauge pressure liquid level sensor
https://www.sensorsone.com/hydrostatic-liquid-level-sensors/


Electrode water level sensor
http://www.gemssensors.com/level/warrick/conductivity-based-liquid-level-control

Optical water level