DIY Pump Flow Sensor (for automated control system)

Dougo

Member
Hi,
I want to detect that the pump has primed properly, so wish to put a flow sensor in the pump outlet line.

I am setting my house up to be ´Smart´. I have an EV, & heaps of Solar, so want to automate the pool
filtration as well, but as I might not be there, I need to ensure the pump is not running dry.

fyi, I am using a home-built version of a ´Liquidator´ that I built in 2016. I am now using ´Cocky´ valves,
a 318 stainless float valve that I modify as a NC valve for the lower valve. Problem is sometimes the scale
builds on the lower valve, causing it to stick. This can stop the pump priming, hence the need for a flow detector.
(btw, the Cocky valves a a great piece of Australian made kit: I use 3/4¨ valves, the smallest.)

My intention is to use an ESP8266 board (wifi) to communicate with my EmonCMS server to log the water flow,
then turn off the pump if no flow detected. (fyi, Emoncms is a database system for a smart energy, etc monitoring system)
I will either build my own vane, with a reed switch or use a commercial switch such as the GE-313 (which is a bit expensive).
Hopefully, someone will suggest a suitable switch I might use

regards, Doug.
 

Dougo

Member
I have just ordered these:






WFS27 G3/4" Female Thread Connecting Water Paddle Flow Switch/Sensor Water Lack Protecting Switch 250VAC 1A
They are PPO plastic, which on my investigation is OK with Chlorine (at least at pool levels).
My thoughts now are not to use a Wifi board, but to power the pump with a 10 minute timer (ie that drops power after 10 minutes),
so by then the Flow switch should have flow established, so all I need to do is continue power with a relay.
The Pump power will be remotely turned ´ON´ on a separate power circuit (that will be controlled by Emoncms).
I am a retired Technician, so it will be IP68 rated, with isolated LV to the switch. It will be some time for the switch to arrive, but I will
detail how it is wired & built when the parts arrive.

regards, Doug
ps: Keep safe from the dreaded Covid! Lucky me in a Covid free area in Sunny Australia.
 

CRAD_oz

Well-known member
Jan 13, 2020
54
Sydney Australia
I was going to suggest a paddle type Flow switch and not a Flow sensor but looks like you already picked it. A paddle switch is either on or off as long as it switches below your lowest flow setting and easy to test if problems occur.
The paddle on the one you have attached is 70mm long but it looks like it can be shortened? will you have enough space to install it in a 40 or 50mm pipe?
I had a quick look but I couldn't see a pressure rating on the switch either. Its a good idea to install gear with a pressure rating over what your pump puts out to be safe.
 

Dougo

Member
Thanks, Crad.
I am only interested in checking the pump is pumping. I have a Davey Multi-speed pump (which has been very reliable & is now years old). It normally runs on mid speed so there is enough flow to run the (clone) Liquidator chlorinator (fyi, if the oz means Aus, the liquidator runs a little water from the pump pressure side, through the top of a tank where the chlorine sits in a layer on the bottom, & water is taken to the inlet side of the pump through a NC valve & a flow restrictor. The bypass water picks up enough chlorine to chlorinate the pool. Works reliably except the NC valve tends to scale up after time, then stick.)
 

Katodude

Silver Supporter
Aug 22, 2017
1,188
West Palm Beach/Florida
Your other option is to get a pressure transducer and attach it to your filter. If you are getting pressure then your pump is running. Also depending on how much pressure you can double check how fast your pump is running. Or if you filter needs cleaning.
 

Dougo

Member
Thanks Kato. The problem with Transducers is it would be running in a hostile environment. This can be circumvented by isolating with a diaphragm (Synthetic rubber mounted between 2 flange fittings, with distilled water on the sensor side), but the mechanical solution should be reliable because it uses reed switches & a magnet.

Also I get really bad scale on my pool plumbing. This might be because I run a Silver Ioniser, but I am not sure. btw, I am not on mains water, or spring, so we practise water conservation. This is one reason I do not use Cyanuric acid: It builds in water until it requires diluting. My pool is covered with shadecloth, so does not suffer from direct sun. When I first started the Silver/Copper Ioniser, we got a lot of brown scum. Once this was scimmed off, it never recurred. Still not sure what it was. In a 50000L pool, we use about 10L liquid Chlorine/week. The water rarely tests under 1ppm chlorine.
regards, Doug
 

Katodude

Silver Supporter
Aug 22, 2017
1,188
West Palm Beach/Florida
Whatever works for you is great. The pressure transducers are built to measure oil and other types of liquids which I am sure are much harsher than you pool water.

Here is one that a few people use.