I have built a system which uses water from a rainwater butt to refill the toilet cistern. I have a pond pump at the bottom of the butt, a valve (because when full the water in the butt is higher than in a full cistern, without the valve it would siphon), and a flow detector. If there is no flow then it will turn on a valve from the mains water. I want minimise running the pump when there is no water in the butt.
My problem is that this is rainwater so it tends to cause an algal film wherever it goes which can stop things working. To sense the flow I have used two different types of impeller systems. The first was optical but that failed fairly quickly when the optics were covered by the film. The second used a magnet/hall effect to detect motion of the impeller but this failed when there was enogh muck to stop it rotating.
I have just tried a flow switch (described as self-cleaning) which has failed, blocking the flow of water.
The pipe the water is in is about 8mm o/d and is plastic. I need a way to detect flow in this pipe that won't be disrupted by algae. Any ideas?
My problem is that this is rainwater so it tends to cause an algal film wherever it goes which can stop things working. To sense the flow I have used two different types of impeller systems. The first was optical but that failed fairly quickly when the optics were covered by the film. The second used a magnet/hall effect to detect motion of the impeller but this failed when there was enogh muck to stop it rotating.
I have just tried a flow switch (described as self-cleaning) which has failed, blocking the flow of water.
The pipe the water is in is about 8mm o/d and is plastic. I need a way to detect flow in this pipe that won't be disrupted by algae. Any ideas?