I'm a mechanical engineer with very few knowledge in electrical so your help is very appreciated.

I'm doing a small project which require to automatically the fill and empty a sink.

How can I automate the filling of the sink, make it stop (so the sink don't overflow) over a long period of time.

I've experimented a little bit with solenoid valves, but they get very hot (and I fear that they melt) if powered more than a few hours.

Here is the valve I used. I know I should probably use a Normally Open one.

Once again, your help is very appreciated.


I will ask my question differently. How can I have a Normally open solenoid valve closed indefinitely?

  • \$\begingroup\$ which voltage are you using to activate the valve? \$\endgroup\$
    – berto
    Commented Jan 20, 2019 at 20:59
  • \$\begingroup\$ How long does it take to fill the sink when the valve is open? How long till it is necessary to refill the sink? Note that it is normal to have two water level sensors (or one that exhibits a large amount of hystersis) in an application like this so that the filling mechanism is not flopping on and off near the filled level. The upper sensor is used to turn off the fill mechanism whilst the lower one is used to turn it on. \$\endgroup\$ Commented Jan 20, 2019 at 21:03
  • \$\begingroup\$ Evaluate the time open and time closed then see if N/C or N/O or a mechanically controlled valve would be energized less.. \$\endgroup\$
    – Solar Mike
    Commented Jan 20, 2019 at 21:10
  • \$\begingroup\$ Hello, it is 12 V to activate the valve and 270 mAmp \$\endgroup\$
    – user210482
    Commented Jan 20, 2019 at 23:45
  • \$\begingroup\$ Welcome to EE.SE? Asking for recommendations for specific products or where to buy them are off limits for this site, so I removed them from your question. Now the answer becomes trivial: you keep the valve closed indefinitely by providing power to it indefinitely. \$\endgroup\$ Commented Jan 21, 2019 at 0:12

2 Answers 2


There are several different types of valves available. You have already discovered solenoid valves - most common are Normally Closed but Normally Open and combination Normally Open & Normally Closed are also available.

There are also motorised valves available. Again - you can fabricate your own using a large hobby servo positioner attached to a ball valve or purchase one ready-made.

Detecting water level is possible using any of several different techniques. You can fabricate or purchase float switches or measure the weight of the water in the vessel or use conductive probes to detect the presence of water.

You will find float switches in most dishwashers and water weight sensors in clothes washing machines.

Your best bet going forward is to research some of these options, then return here and modify your question with more information. We will help.

  • \$\begingroup\$ The best would be an 1/2" NO valve or an motorised valve but I'm having a hard time finding a place selling ones. Could you recommend me a website selling some cheap ones and shipping to Canada? \$\endgroup\$
    – user210482
    Commented Jan 20, 2019 at 23:47
  • \$\begingroup\$ It's been a while since I purchased valves. I would check eBay, aliexpress, deal extreme, banggood. \$\endgroup\$ Commented Jan 21, 2019 at 2:58

Here's an update. It is very hard to find a normally open valve for cheap (not frequently used in industries I guess) so I could fix the problem by decreasing as much as possible de voltage of the valve. I could activate it at 10.5 V instead of 12 and I could decrease the voltage until 6.5 V. What I will probably do is used a few capacitor to be able to reach the 10.5 V and then maintain it at 6.5.

Thank you for your help!


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.