WHO USED ALL THE HOT WATER!!! Need a simple temperature data logger ** UPDATE **

[Brumby]

Scenario: "Who used all the hot water?!!!" - typical domestic situation.

My idea is to have a temperature sensor mounted on the main hot water pipe before it splits off to the various taps, with temperatures recorded at regular intervals, including timestamp.  This will show when hot water was used - and for how long.

I've looked at various offerings and an off-the-shelf example which appears to have the functionality that will serve the purpose is the Inkbird TH2, which captures the data and allows me to monitor via bluetooth - which is enough.

However, I am uncertain as to whether it will operate completely stand-alone.  I could possibly tolerate a one-off registration exercise, but I DO NOT want internet dependence for ongoing function.  Not at all, never, ever.  It's a completely unnecessary restriction for what I want to do.
 
General reading hasn't made it clear at all. 

First concern is whether my old Galaxy S5 would be able to run the app, so I downloaded the App and installed it.  So far so good.  Then I started looking for the T&Cs.

I found the set up path through the App really oppressive.  It seems you cannot proceed without entering into a subscription for all the "really good extras" (NONE of which are of any interest for this exercise) - even if it is just the 3 day free period.  Of course, you can "cancel at any time" - but that's a dance I'm not at all keen about.  It also asked for permissions that I really didn't want to give it and weren't necessary for what I wanted.  And then there is the Privacy question.

So, I found the T&Cs and came across a couple of details that stopped me in my tracks.  Specifically (and I paraphrase):
 1. You must accept all updates
 2. We do not guarantee the App will continue to work
That just wreaks of the potential for a problem that I have already encountered in other Apps - where the App is updated to the point where my hardware and O/S are no longer capable of running the App.  (Don't anybody suggest I should buy a new phone.)

Options:
1. Just buy it and see how it goes (price range AUD$20-30 internal vs external sensor)
2. Buy it and see if I can write an App of my own
3. Build a DIY project. (Is there a design available, with code?  I could do it myself, but I don't have enough time to do the things on my list as it is.)
4. Suggestions.....

[floobydust]

When I was young, my dad used to use up all the hot water so I would close the valve on the hot water supply until I heard him cuss and swear and leave the shower. Then I had a chance of a warm shower.
Once I lived with a roommate that was first in the shower in the morning. He would then fall asleep leaning against the shower wall, until he used up all the hot water... and the cold water then would wake him up. He would fall down and I knew after the big kabang, my turn in the shower next and it was going to be cold. I almost murdered him.

I think you need to know the water heating system's status, on/off and log that as well? In Canada we use a hot water tank that is heated by natural gas. So a household always has at least 40L of hot water but once that is used up there is a "recovery time" to heat it up again, that is often a good portion of an hour. You wouldn't know where your system is at only by looking at temperature.

Is your water heating gas or electric or solar? The reason I ask is a common problem with a hot water tank is the dip tube (and sacrificial anode) corrodes. So incoming cold water no longer comes in at the bottom, but instead at the top of the water tank where the outlet port is. You end up with a hot water tank that acts like it has low capacity (cold water) at high flow. Also, plumbers don't use galvanic isolators properly causing premature corrosion.

Just to make sure your system works, instead of the long Hollywood showers being the problem.

[vad]

Tankless water heater is one of the best solutions.

[IanB]

Tape a thermocouple to the pipe and use a data logger?

Simplest option, use a logging multimeter like a Fluke 289 or an EEVblog 121GW, leave it logging for a week and then dump the data.

Less simple option, use a single board computer like a Raspberry Pi and have it log onboard or have it send the data to another computer over wi-fi.

I guess you will need cooperation of the residents, or they might simply disconnect the logger. But if the residents are cooperative, why not simply ask them who used all the hot water?

[NiHaoMike]

Try the simple solution of partially closing the valve? Then it would take longer to use too much hot water.

[KE5FX]

Or just raise the temperature. 

[Zucca]

Tankless water heater is one of the best solutions.

Until the teenager daughter will brake daddy bank causing astronomical gas bills.

[Brumby]

Additional information prompted by comments...

1. The tank is only a couple of years old and there is no indication of any fault - just excess usage.  Partially closing the tap at the outlet would reduce flow.  While that is an option, it does not address the principle issue.
2. I will have NO difficulty fitting anything as the head of the household has raised the request.
3. The principal issue is determining how much hot water is being used - and by whom.

Identifying the individuals can be worked out from timestamps.  Time of day and duration can be easily determined and this will probably be adequate for the basic need.  The actual flow is a secondary issue as it seems the main offenders simply turn the hot tap on full and regulate with the cold.

Getting a finer take on actual flow rate would require a bit more finesse.  In that respect, the temperature drop over an exposed section of pipe would be useful: A greater drop means a low flow rate, while a lower drop would indicate a high rate.  To do this properly I would need two sensors and some calibration experiments ... which could be a phase 2 exercise.  Absolute litres per minute is not an objective, so let's not head down any paths that require plumbing.

[Brumby]

Tape a thermocouple to the pipe and use a data logger?

This is the basic idea.

Simplest option, use a logging multimeter like a Fluke 289 or an EEVblog 121GW, leave it logging for a week and then dump the data.

I don't like the idea of leaving a bit of kit like that lying around - besides the head of the household won't know how to access the information and I do not want to get into data retrieval duties.  Having an App with Bluetooth or WiFi connectivity is the direction that makes sense, especially when accessing the information needs to be, essentially, in real time - typically within an hour of occurrence.

Less simple option, use a single board computer like a Raspberry Pi and have it log onboard or have it send the data to another computer over wi-fi.

This was my thought for a DIY - but I don't really have time for development.  If someone has already built something and shared it, I could manage construction.

I guess you will need cooperation of the residents, or they might simply disconnect the logger.

<Answered above>

But if the residents are cooperative, why not simply ask them who used all the hot water?

They lie

[tautech]

3. The principal issue is determining how much hot water is being used - and by whom.

Do be aware if your Powerco can control HWC's remotely it may be just not being heated.
Better to monitor the power supply to the cylinder too.

[RoGeorge]

Temperature alone won't tell the amount of water.  For that, you'll need a water calorimeter, which accounts for both the water temperature and the debit.  And that still won't tell who used all the hot water, unless you add webcams at the girls college dorm showers. 

[AndyBeez]

Day 22 in the Big Brother household and someone has used all of the hot water. Angry housemate Nikki is in the Diary Room...  Politics and comedy aside, this scenario suggests you guys have heating system that is not fit for purpose. What are you/they paying for?

 Google for Bluetooth data logger.

[Brumby]

Temperature alone won't tell the amount of water.  For that, you'll need a water calorimeter, which accounts for both the water temperature and the debit. 

Absolute accuracy is not required - simple relative comparison will suffice for the basic requirement.  When and how long is enough for them.  I was considering the temperature gradient idea as an extra indication.

And that still won't tell who used all the hot water, unless you add webcams at the girls college dorm showers. 

That is not a problem I have to address.  If I simply make the times known,  the head of the household can work that out.

[ejeffrey]

  The actual flow is a secondary issue as it seems the main offenders simply turn the hot tap on full and regulate with the cold.

I'm not sure what plumbing fixtures you have but that's not generally how it works.  The flow is mostly regulated by the shower head. The tap handles set the blend ratio if you open the hot water tap full and then open the cold water tap to set the temperature the hot water flow will decrease.

That said it probably doesn't matter.  Assuming people are actually in the shower and not just letting the hot water run to make a steam room there is a fairly narrow range of water temperature most people will tolerate so a simple on timer is probably going to be accurate enough.

I'm not sure how fast the pipes cool down after the water shuts off and how much that might complicate your measurement.  Another possibility would be a microphone or vibration sensor to detect if water is flowing in the hot water pipe.

[themadhippy]

the head of the household has raised the request.

but I don't really have time for developmen

surely you can use the development time to your advantage to get out of other ,less intresting duties.
"we need to go shopping/visit the inlaws/sort the garden"
"loved to,but i really want to get this temperature logger finished that you said was urgent"

[coppice]

Tankless water heater is one of the best solutions.

Until the teenager daughter will brake daddy bank causing astronomical gas bills.

The bathroom repair bills after she causes anything not solid plastic, metal or glazed to peel or blacken with mould can exceed the gas bill.

[Zero999]

Tankless water heater is one of the best solutions.

Until the teenager daughter will brake daddy bank causing astronomical gas bills.

The bathroom repair bills after she causes anything not solid plastic, metal or glazed to peel or blacken with mould can exceed the gas bill.

Why would that happen with an instant hot water heater but not with a hot water tank?

[Rick Law]

..
My idea is to have a temperature sensor mounted on the main hot water pipe before it splits off to the various taps, with temperatures recorded at regular intervals, including timestamp.  This will show when hot water was used - and for how long.
...
4. Suggestions.....

I assume your "main hot water pipe" is where hot water exits the water-heater or very near it.  I will call it "main pipe" as abbreviation.

Depending on how your plumbing is routed, "main pipe" may not be the best spot.  You have more factors to consider -- (1) hot water still in the system when water tap is turned off and (2) where the hot water is going.

Easy way to clarify is to lay down a scenario:  Let just say, you are taking a shower military-style (at or under 2 minutes).  5 minute after your shower, someone turn the hot water in the kitchen for 1 minute to rinse a cup.  Now the "main pipe" is re-filled with freshly heated water again before it was cooled measurably after your shower.  Say another 10 minutes later, someone washes his/her hands in the second bath-room, now the main pipe is re-filled with hot water again.  So on, each time the hot water is used briefly, the "main-pipe" refills with hot water and it may not cool for a very long while.

The best position would be at the shower-head, there temperature alone will work.  Otherwise, you have to know the cooling time of still-water in the pipe, and consider any "branching" to another outlet.  Note also, if the shower room is high such as in the 2nd floor while the water heater is in the basement, there are a lot of pipes holding the not-running but still hot water.  The hot water will rise to the highest point it can even if the hot water is not running.

Edited to add this:  For cooling time, you also have to consider ambient temperature around the pipe.  I am sure it will change a lot on a hot day verses the cool evening after sun down.

[coppice]

Tankless water heater is one of the best solutions.

Until the teenager daughter will brake daddy bank causing astronomical gas bills.

The bathroom repair bills after she causes anything not solid plastic, metal or glazed to peel or blacken with mould can exceed the gas bill.

Why would that happen with an instant hot water heater but not with a hot water tank?

Er, isn't that obvious. So many of them only stop showering when the water runs cold. Continuous hot water means they steam up the bathroom until it falls apart. If you have a really effective extractor fan you can stop it, but in the winter that means you are exhausting a lot of expensively heated air, so going wild with the extractor was more for when we lived in a hot and super humid climate.

[ywara]

I think you need to take a step back and look at the problem statement.

The problem statement: There isn't one. Domestic bickering about lack of hot water or energy consumption isn't really a problem of hot water or energy consumption, but a problem of bickering. Bickering is a problem without a solution.


So there are two ways to approach this, I think.

1. Monitor who is using hot water. I suggest RFID tags attached to all persons. Combined with sensors on the various faucets, shower valves, toilets (if you have hot water plumbed to your toilets), washing machines, etc. you can track who is using what. In many cases you should be able to adapt simple limit switches. In high-flow applications (e.g. a bathtub) you may need an angular position sensor on the blending valve or hot water valve.

2. Monitor hot water demand, and correlate with potential culprits. Install cheap wifi cameras in or near bathrooms, kitchens, and laundry rooms. Add simple digital datalogging to your hot water heater(s). When they are on, hot water is being produced since it was recently depleted. You can easily correlate the users to the demand.

I suspect #2 is more practical for small households. Perhaps 8 people or less. #1 will scale better to large families into the hundreds.


Both of these options probably result in family counseling or court. Tread carefully, but sometimes victory is worth it.

[Kim Christensen]

Put a fake webcam high up in the shower stall. Put a sign next to it that says, "Webcam activates 10 minutes after water is turned on"... Have a motion sensor that turns on a red LED on the "cam" after 10 minutes of motion.







EDIT: It's a joke!

[SiliconWizard]

Put a fake webcam high up in the shower stall. Put a sign next to it that says, "Webcam activates 10 minutes after water is turned on"... Have a motion sensor that turns on a red LED on the "cam" after 10 minutes of motion.

Uh huh, nothing worse than "lying" to close people. Once they figure out the lie (which would probably happen pretty fast), they'll stop trusting you or even listening to you in any serious way altogether.

[tautech]

There are many fish hooks in a problem like this.
1. Already mentioned that Powerco's manage their demand by switching water heating loads.
2. Hot water storage capacity is insufficient for the demand.
3. Mum did a large load/s with the washing machine that day.
4. Heating regulation settings are just too low for the capacity/demands.
5. The plumbing installation can be substandard with long runs to each HW draw point wasting HW just supplying each outlet. Smart systems use a constant return system to have HW instantly on tap.
6. While there are often local regulations as to how hot water heating can be set these can be overridden with the installation of a tempering valve at the HWC outlet that mixes cold to maintain a constant and safe HW temp for consumers.

Addressing any one of the above can have problems miraculously vanish.
Engage a smart/experienced plumber for a fix.

[Someone]

I'm not sure what plumbing fixtures you have but that's not generally how it works.  The flow is mostly regulated by the shower head.

Which is usually the easiest/cheapest way to balance hot water demand, replacing the tank with a larger unit is $$$ but replacing the shower head (or changing its restrictor) with a very low flow will also balance the supply vs demand.

Can get a practical shower from 3-5l/m, but some people will remove the restrictors and "enjoy" their 20-30l/min (4-10x difference in consumption/cost/energy/etc).

My idea is to have a temperature sensor mounted on the main hot water pipe before it splits off to the various taps, with temperatures recorded at regular intervals, including timestamp.  This will show when hot water was used - and for how long.

4. Suggestions.....

The "proper" industrial solutions work offline and are easy to deploy (would suggest putting the thermal sensor at the grey water exit, as temperature rise will then be a proxy/estimate of the flow rate at the time) but are $300/400/500 units. Solution is to have the people in question work with each other.

[vad]

Tankless water heater is one of the best solutions.

Until the teenager daughter will brake daddy bank causing astronomical gas bills.

The bathroom repair bills after she causes anything not solid plastic, metal or glazed to peel or blacken with mould can exceed the gas bill.

Why would that happen with an instant hot water heater but not with a hot water tank?

Er, isn't that obvious. So many of them only stop showering when the water runs cold. Continuous hot water means they steam up the bathroom until it falls apart. If you have a really effective extractor fan you can stop it, but in the winter that means you are exhausting a lot of expensively heated air, so going wild with the extractor was more for when we lived in a hot and super humid climate.

Exhaust fan, smart switch, humidity sensor, and home automation are the way to go. Throw in a door stopper to keep the bathroom door open when not in use; it'll help save a few dollars on the running costs of the whole-house humidifier during winter.