DIGITENFS-C01 G1/2" BSP Male Thread Brass Water Flow Switch with Filter 1-30L/min, 0-2A/ 0-220V(AC or DC)

works fine to turn on my relay, to power my hot water heater elements.

The 1st one I ordered did not work properly, Amazon sent a replacement quickly and that one works well. You will need the 3/4" adapters to go from UK to USA. Be sure to seal the threads to the adapter real well. My 1st attempt had a small drip. Needed to disassemble and use Teflon tape + thread sealant compound to get a leak free seal. It's operating well as of today.

I tested it on an ohmmeter, and it worked great. Then, I hooked it to 120V (half voltage) and 0.2A (1/5 current max rating, likely much less) = 1/10 its rating, and the "switch" remained closed.(TOO) MANY OTHERS REPORT THIS EXACT SAME FAILURE!!!!!It works like this: Two opposing magnets in the tube are forced together by water flow. So far so good. But outside the brass walls, this magnetic field is very weak. SO - the magnetically actuated reed switch must be weak. And should there be any current surge (in my case a power supply - BUT - well within specs) the reed switch contacts stick together.If you're to use this, use it ONLY at very low voltage and current. You'll likely need to use a DC circuit driving transistors to then drive a relay that then drives the 120 or 240 circuit. Otherwise you simply can't rely on this at all.

Threads are non-standard but I was able to adapt using a C-PVC fitting having a rubber seal inside. The switch stayed open on the first install (horizontal). I suspect if had some debris in it. Tried again in vertical flow up position and now it works fine. I used it to trigger a relay to disable a peroxide pump for outside water usage.

Don't make the mistake of connecting a magnetic reed switch directly in line with power as that will either damage it immediately or it just won't last. Instead, connect it to the “trigger wires” of a relay. The following configuration works:1. Purchase a delay relay that has a Continuous Trigger Signal mode.Example: XY-WJ01 Programmable Relay https://www.amazon.com/gp/product/B081N5NG8Q/ (Mode 8)2. Connect the DIGITEN switch wires to the red and black Trigger wires3. Connect power to the relay, set it to Mode 8 (don’t set any times) and connect the loadWhen the DIGITEN switch closes, which holds the Trigger wires closed, the relay operation will start and continue until the Trigger wires are open again. The micro voltage of the trigger signaling places less stress on the reed switch and it should last a long time.

Going to give the goods on this as well but want to get straight to the point for those who are buying in the US.This product is advertised as BSP. There are two types of BSP. BSPT - Taper & BSPP - Parallel - which is what this is SUPPOSED to be. This means the diameter at the very beginning is exactly the same as the diameter at the end. Unlike National Pipe Thread that has a taper, BSPP does not. That would still be solvable with NPT adapter and a washer and/or pipe tape/joint compound (as indicated in the product description.The problem is that the threads on the one I received were not cut with a BSPP die. The threads are perfectly square instead of having a 55deg angle. See the picture attached. No angle on the thread.A female NPT adapter should thread onto a male BSPP without issue - it just won't seal well.But my 3/4" female NPTs will not thread on even 1 turn of threading because the threads are square instead of angled. Maybe I got a bad one - as others have indicated success with teflon tape...As far as the GOODS go.This product should be exactly what I need. A low flow sensing valve. It is pretty slick the way it works. There is a plunger (object on right in second photo) that seats against the input end of the tube. When even a small amount of water flows, this plunger slides towards the outflow end. There is a magnet on the output side of the plunger and the external mounted sensor can sense this magnet through the brass, closing the circuit. This is NOT a hall effect flow meter. Just a magnet moving inside the pipe.But the beauty of the design is that there is no penetration thru the brass body. Magnetism works through brass - so the sensor switch never touches the water.Also clever is that the retainer nut (on the left) also has a magnet in it. The magnets are oriented such that they repel each other. The plunger moves forward and the retaining nut magnet pushes back. No spring to clog or corrode! When flow stops, the magnet is strong enough to push the plunger backwards and the switch is deactivated. The plunger moves about 1/4" which is enough to activate the switch. And as soon as the pressure is released, the other magnet repels strong enough to seat the plunger back in the circuit Normally Open position.A couple of other notes that are neither a features or a detractor.s Just something to realize. The plunger does not have a seal so when it is seated a very small amount of backflow is possible. This is NOT a check valve. That being said - it will not allow A LOT of flow backwards. In my application, I need to sense flow out of pressure tank. But water has to flow back into the pressure tank as well (at a slower rate). So this MIGHT have restricted the flow rate for the tank to fill - but since I never got that far I cannot confirm. I just can tell with air flow that flow is restricted in the reverse flow direction.The arrow indicates flow direction. This will absolutely work with the arrow parallel to the ground. It will likely work with the arrow pointed up but won't be as sensitive to flow rate because the flow has to lift the weight of the plunger. It MIGHT work with the arrow pointed down because the repeller magnet seems to hold the plunger in place on my bench and the switch does not close. But it takes very little force to move the plunger since the weight of the plunger is pulling "down" and the repeller magnet is pushing all the time. If the strength of the permanent magnets ever weakened, it might not be enough to hold it in the open circuit position.Should be 5 stars as it is a simple and practical flow switch - but with the threads cut incorrectly, I have to drop it to three. Even if I had a BSP adapter - I don't think it would thread on because of the square cut of the threads. Square threads are normally for machine drive parts - so either the die was damaged or someone really didn't know what they were doing when the turned up the threading machine.

It works well. I had to buy two 3/4” G Thread (BSP) Female to 3/4” NPT Male Connector (like ASIN B0B74F451Y).It is very difficult to get the connection not to leak, even with a lot of Plumber's Tape between the flow sensor and the BSP to NPT adaptor. However, I inserted a hose washer in between and did not need Plumber's Tape. No leaks. See photo of the hose washer. Use this one , not the orange type because the orange will expand inside and reduce the flow. I read here that some people do not use BSP to NPT adaptor and use a lot of Plumber's Tape. So, a hose washer, may be a solution for that too.

Though this was stressful getting it to my door. This does a great job as on demand inline hot water switch. Saving money by not cycling the boiler through a thermostat. Only running when the tap is turned on.