Water level controller by monitoring water coming through tap

Tonyr1084

Joined Sep 24, 2015
4,894
The problem I have is that water can come in tap at any time during the day for 1/2 hours then I have to detect the flow of water through the tap. when water is detected in that tap the pump turns on and fills the house tank, when the house tank is full a turns off the pump.
OK, if there's pressure detected then a timer circuit is triggered to run the pump for 2 hours (if I'm reading 1/2 hours to mean one to two hours). When the tank is full the pump can be shut off, even if there's supply available. With a sensor and timer, when pressure is detected and the pump comes on the pressure may fall below the level of the sensor. That's why you run a pump for a set period of time - or until the tank is full.
 

Externet

Joined Nov 29, 2005
1,527
That is not the way it works, Tony.
The inlet cistern or 'Sump' or pre-tank you mention is filled from the municipal grid with a plain float valve like toilet tanks have, and no solenoids of any kind. Because municipal supply has no pressure to reach the elevated tank or to eliminate tanks going direct to all faucets as in a developed nation.
But nobody has the inlet cistern. Because the cistern is not a municipal implementation in every house premises. They just get votes cheaply installing pipes.
 

Thread Starter

aspirea5745

Joined Apr 17, 2019
81
OK, if there's pressure detected then a timer circuit is triggered to run the pump for 2 hours (if I'm reading 1/2 hours to mean one to two hours). When the tank is full the pump can be shut off, even if there's supply available. With a sensor and timer, when pressure is detected and the pump comes on the pressure may fall below the level of the sensor. That's why you run a pump for a set period of time - or until the tank is full.
Perhaps I did not explain as image can show , So i am posting the updated image

1593623941135.png
 

Tonyr1084

Joined Sep 24, 2015
4,894
@Externet Excellent point.

Here's what I just banged out: When pressure has been sensed, the pump sucks water until the residential tank (cistern) is full. A float sensor shuts off the pump. If the water level is so low that it does not fill completely, the pump runs for a set period of time. But as you said, if I have a stronger pump than you then I can pull water away from you. Notice the air gap in my cistern inlet port. Nobody can suck water backwards out of my tank.

Granted, there are a lot of civil considerations here. From what I gathered by the original post is that when water is available he can connect a hose and fill his tank. Assuming that to be the case there must be sufficient pressure to fill the tank. If someone has a larger hose they can fill their tank faster. Somehow I don't get the impression we're competing for water, rather, when the authorities make it available, households have to fill their tanks. Or go without water till the next time; which can come at 6:00 AM or 8:00 PM. Or anywhere in-between. And I used those times for sake of reference. Actual times are probably not as mentioned. Even if I can pull water away from others, I can't use more than I can store.

1593624033321.png
 

Externet

Joined Nov 29, 2005
1,527
We are back to the same, aspirea. You are lacking an inlet cistern; which liberates you from any sensors to find if there is water being supplied.
The cistern 'enables' the pump with a float switch when not empty IF another elevated reservoir float senses it is empty.
It is two switches like these, one in the cistern; off when empty, one in the raised tank; off when full :
----> https://www.aliexpress.com/item/32324664005.html
There has to be some water in the cistern and the raised tank should be not full for the pump to work. That will also be legal pumping -not sucking- with no need to connect manually daily.
 
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Tonyr1084

Joined Sep 24, 2015
4,894
You are lacking an inlet cistern
As you DID say, flow into this inlet cistern can be controlled by a float valve. The issue I have with that is the pump. If it pumps faster than the inlet flow, the pump will do a lot of starting and stopping. That may limit the life of the pump motor. OR if the pump is just running until the residential tank is full, as soon as the level drops the pump will come on. Unless there's a low limit trigger point at which the pump starts. But then what happens if you're between full and low? Water becomes available but the pump doesn't run unless the tank has dropped below a set point. It's my opinion that it's better to shut the pump off when the tank is full and not turn it on again unless two conditions are met: The tank is lower than full by some small quantity AND there's water available for the pumping. The timer can turn the pump on when pressure is detected AND the tank is NOT full. Once on, the pump runs for a set period of time, then shut off. OR shut off when the tank is full, and not restart until the next NEW pressure detect event.
 

Externet

Joined Nov 29, 2005
1,527
The choice of pump is not the subject of this thread, but nobody expects to install a domestic fish tank pump nor a ten kilowatt one for the application. The system works in millions of homes worldwide; it is a super proven way to do it, but takes proper tailoring of reservoir capacities, consumption rates, supply rates, pipe sections, which are also beyond the subject.
The starting/stopping feared does not happen as you think because float switches have mechanical hysteresis.
 

mcardoso

Joined May 19, 2020
122
From the way I see it, either of @Tonyr1084's designs can be made to work. I have tried to summarize the advantages and disadvantages. Please correct me if I am wrong.

Pros:
-Disconnect between the pump and the water main
-Pump can run intermittently as dictated by water supply capacity
-Only need relays

Cons:
-Cannot "suck" water from the main. Little to no flow in a low main pressure situation.
-Cistern/Sump must be permanently installed near the house
-Pump must start and stop based on the flow into the cistern/sump (larger cistern/sump helps with cycling rate)
-Requires 3 float switches (Cistern/Sump High and Low level + Tank High)
-Requires a solenoid to automatically disconnect the mains or the cistern/sump will spill water

1593634450106.png
Pros:
-Simple implementation without additional tank or solenoid
-Only requires one float switch
-Pump runs once until tank is full

Cons:
-Potentially illegal
-Requires a moderately expensive pressure sensor
-Pump suction might reduce inlet pressure and turn the pressure sensor off (On duration timer might be needed)
1593634849217.png

I do not think a water presence sensor could be used in the second case as there would always be water in the pipe, even if the valve upstream is turned off. A float switch would be more reliable.

In general, a configuration of redundant float switches would be recommended as they do fail and failure could mean either spilling water for however long the water is turned on for, or running the pump dry and damaging it.
 

Reloadron

Joined Jan 15, 2015
5,605
Given the choices I would to opt on measuring supply line pressure to determine if water was available or not. Your initial drawings showed a roof top tank which isn't unusual in many countries I visited or lived in. While the availability pressure is low there is enough pressure to trigger a switch and water pumped to a rooftop tank where it is gravity fed to the household below the tank. If availability stops during pumping water to the roof a simple flow switch will prevent the pump running dry. Sensing the pressure during availability and pumping may take a little effort and beyond that just a flow switch so you aren't running a pump dry.

Fresh drinking water and plenty of it is something we take for granted here in the US. Living in Cleveland, Ohio we draw our drinking water from a crib located 5 miles (8 kilometres) out in Lake Erie. We have all the fresh water we could want. Like many I have been to countries where water was a precious commodity.

Ron
 

Thread Starter

aspirea5745

Joined Apr 17, 2019
81
It concludes that we need a pressure sensor to detect the water pressure and a float switch in the tank to stop the pump
As you can see the pressure sensor, pump and float are very far apart. If we keep this far, then will it be able to work together?
 

andrewmm

Joined Feb 25, 2011
526
Never-mind the pump and sensors. Just put a float valve in the tank. When the water is low the valve will open. When water is present it will refill the tank. If the tank doesn't need all the water supplied the float valve will shut itself off and no water will be wasted.

[edit] Here's what I mean: When "Community Water" is ON the Residential tank will fill until full. The float valve will shut off any further flow of water and prevent wasting of water. Day or night, whenever community water is available the residential tank will fill. If there's a need for a booster pump - that's a different story.

View attachment 211152

From my limited experience of countries that have this sort of thing, the pressure of the water is no way enough to reach the tank on th eroof.
 

Tonyr1084

Joined Sep 24, 2015
4,894
(On duration timer might be needed)
That's the purpose of the pump control board - to switch on when the sensor detects water pressure above a pre-determined level. Once the pump starts it runs for a set period of time. Initially it could have run for a few hours, but as @mcardoso mentioned - running a pump dry could be a problem. One I hadn't considered. Rather than run it for hours, it cold run for 10 or 15 minutes then shut off. If water pressure is still there it could run again for an additional 10 or 15 minutes.

In my system there WILL be a period of time when the pump is running with no water in it. From your depiction it looked like a centrifugal type pump. So how ever high the water has to be pumped to make it up to the rooftop tank the pump you already have is sufficient for the task.

As far as any legal issues with a pump sucking water from the main line - - - that would depend on your local government or whomever is operating the water tower.

From my limited experience of countries that have this sort of thing, the pressure of the water is no way enough to reach the tank on the roof.
Haven't heard that from @aspirea5745. is that the case? We ARE trying to solve a problem without knowing all the parameters we're dealing with.
 

andrewmm

Joined Feb 25, 2011
526
So my suggestion

Assuming you have access to "the tap"

a) Plumb the tap into a small tank , using a ball cock to turn off the flow of water when this first tank is "full"
lets call this the pump tank.

b) sensor on the Pump tank , a flat switch, that detects when the pump tank has enough water in it to pump, and a second one that detects when water is low.

c) Second tank on the roof, has a float switch for when its full., lets call this the roof tank.

So like this , when there is water, the pump tank will fill up , controlled by the ball cock ,

A circuit, relays circuit would work, that when the pump tank has water, and the roof tank i s not full, the pump operates.


Can some one do a picture / schematic for the chap please ?
 

ElectricSpidey

Joined Dec 2, 2017
1,192
A system like this has already been suggested twice and apparently rejected. (but without the electronics)

A pressure switch seems to be the preferred way, but I still wonder what happens to the pressure when the pump is running...I predict oscillation.
 

Tonyr1084

Joined Sep 24, 2015
4,894
I predict oscillation.
So do I. ON - OFF - ON - OFF, every full second or two. On long enough to pull a vacuum then shut down and coast to a stop (depending on the type of pump), then back on again. Eventually (and not in a long time) the motor will probably fail from such an oscillation.
 

Alec_t

Joined Sep 17, 2013
11,505
I still wonder what happens to the pressure when the pump is running...I predict oscillation.
I think you could avoid that by using a toggle circuit. Initial inlet pressure rise sets the toggle. Pump starts. Pressure reduces but is measured as 'running pressure'. Toggle is reset and pump stops when either tank is full or running pressure drops close to zero. Sourcing a suitable pressure sensor would be key.
 

ElectricSpidey

Joined Dec 2, 2017
1,192
Sure, electronics would make a pressure switch a doable system, but simple systems with no electronics have been offered, and in use around the world already.
 

Tonyr1084

Joined Sep 24, 2015
4,894
A pressure sensor on the pump output will tell the control board there's water pumping. When water becomes unavailable the outlet pressure should drop and shut the pump down so it doesn't run on. Depending on the head pressure (how high the water is being pumped) the pressure sensor would have to be high enough to not see water resting on the pump and to also sense a drop in pressure due to a lack of supply.

[edit] A back flow valve or back flow preventer can be just above the pump. When water is no longer available the pump starts sucking air. The weight of the water in the up-pipe (pipe going up to the tank) will close the valve and the pressure will drop in the pump housing. That drop in pressure can signal the pump to shut down.
 
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