Velleman liquid level controller kit velleman k2639 there are times when too much water can be a problem just as there are occasions when too little can leave you in trouble the velleman liquid level controller is the solution with this kit you can build a device which monitors levels to warn you if your water tank is close to overflowing or running dry it can indicate low middle and high levels automatically switch a pump to keep the right fluid level and if the sensor detects a level