I forgot to mention, this problem is solved. It mysteriously fixed itself. After unplugging a connector and reconnecting it, the sensor started working again.

Are you certain you were looking at information for your specific unit

No, I don’t have the tech details for my specific model. Both videos cover different models of the same brand. The first video (d8ucufoyUlQ) model in the video looks newer judging from the control panel but interior looks the same. The 2nd video (G4bO8MYqQKk) has a different looking interior with a black label on the pump, so I think that’s an older one. I was figuring if a newer and older model both have the same voltage specs then mine is probably the same.

The voltmeter was set to DC voltage, 20 V (which should measure up to 20 V). My meter does not have a frequency function (Hz), so I don’t have the benefit of checking to see what flow rate is measured.

I should also mention that my cold water flows at ~1 liter/5 seconds and the hot water circuit flows at ~1 liter/7 seconds.

(update)
I found the service manual… did not realise I had one. But it’s not too useful. It does not clearly describe the relationship between voltage and state. There seems to only be a diagram which I posted here:

https://lemmy.dbzer0.com/post/26703241

Thanks for the feedback. Indeed that seemed to be the best theory. So I found these quite useful videos:

• https://iv.ggtyler.dev/watch?v=d8ucufoyUlQ
• https://iv.ggtyler.dev/watch?v=G4bO8MYqQKk

My voltmeter detected 4.68 V on the red input wire showing that the sensor is well fed. The green “signal” wire is supposed to be 0 V at rest and 2 V with water running. In my case the green wire is ~1.33 V at rest and ~0.66 V when water is running. That’s bizarre, no? As I understand it, a magnetic fan spins when water is in motion which generates a current in magnets around the fan each time the fan blade (impeller) passes a magnet. I can imagine that a faulty impeller or sensor would reduce the voltage when it spins, but bizarre that the voltage would be 1.33 V when the water is still.

I suppose either way the sensor and impeller will need to be removed together since they are part of the same fitting. From there I’m not sure which one to replace. Hopefully it’ll be visible.

Anyway, thanks for the reply!

You want to open the hot valve 100% until the hot water comes because it conserves water. You want to clear out the hot water line as fast as possible. Turning it to 70% just takes longer to heat up and you’re just dumping cold water out for no reason.

This is precisely what a thermostatic valve gives you. I don’t think you know how a thermostatic valve works. If the thermostat on the mixer bar is set at 38°C and you turn on the pressure control when the water in the hot line is cold, a thermostatic valve opens the hot 100% immediately and when the hot water arrives at the fixture it automatically adjusts. What you say about starting 70% open is exactly the problem you have when /not/ using a thermostatic valve, like the pressure balance valves that are common in the US.

(edit) also consider how tankless heaters have a minimum threshold for turning on. If you open the hot valve just a little, the heater will not be triggered. It must be open enough to trip the flow switch. It can be tricky to open the valve just enough to trigger the heat. A thermostatic mixer valve solves that.

Even a couple of dollars more for a contractor is a lot when a thermostatic valve doesn’t add any value.

I don’t think you saw the pic I posted of the cheap thermostatic mixer bar. Those can be installed by anyone because they are external. You just turn two union nuts until hand-tight then give ¾ turn extra with a wrench.

The bolts use a plastic washer and plastic nuts that slide into plastic rails of the plastic cistern. It’s really flimsy. As I tighten the nuts, I can hear the cracking sound of the plastic washers cracking internally. I’ve reinforced them with a bit of thin sheet metal but whatever I do cannot rely on bolts to add much pressure. This is also why I kind of doubt a rubber flanged gasket working even if I could track one down.

But indeed using all gummy stuff would likely work (but messy!). I’ll try it if my next plan fails.

In US the most common type of seal is a wax ring.

I’ve seen those used between the toilet and the floor on US toilets. I didn’t know they also used them between the cistern and bowl. That might work here but finding one locally seems unlikely but I’ll have to look anyway.

But everything needs to be extremely rigid, any movement later will break the seal.

Well, cistern is plastic and flimsy so maybe it wouldn’t work. I’m also thinking the hard rubber gaskets might only work well for a heavy ceramic cistern.

I appreciate all the recycling tips. People around here just use them to decorate street corners without cleaning them up first. I never see them getting dumped, so I guess the city porcelain beautification project must be happening late at night.

One practical use I might consider is for the parking competition. Sometimes people try to reserve street parking by putting junk on the street in front of their house until they need to park. A heavy old ceramic toilet might work well for that as probably no one else would want to touch it to take a parking spot.

I just removed the cistern for like the 6th or so time to inspect. The gummy stuff appears to adhere very well to both the ceramic and the foam. I would be quite surprised if the water were getting between them. I suspect the most likely theory now is water goes between the foam and the cistern and over top the foam. To test this, I guess I will cut out a paper ring and place that on top of the foam and see if part of the paper gets wet. If the paper gets wet, then I’m thinking I will wrap electrical tape around the cistern down spout to widen it a bit, to get a tighter fit in the foam ring, and maybe put 1 strand of jute (rope) under the electrical tape near the top. And if that fails I guess i will put some of the gummy stuff on the top of the foam, though that will make for a mess everytime the cistern needs to be removed.

It’s bizarre that thermostatic mixers are costly in the US. I can get a new one as cheap as €25 if I shop out the sales, or probably €10 2nd hand.

Tankless water heaters are really lagging as well in the US, and absurdly costly. I’m sure that will get corrected eventually. But in Europe tankless boilers are the norm and used in combination with thermostatic mixers. The lack of tank causes a delay in hot water because it’s less instant than a pre-heated tank. The heating element takes time to fire and reach a high temp. So you are even more tempted to open the hot valve 100% until the hot water comes, which means you have to diligently readjust the valve to avoid scalding.

The luxury fix to that delay is to have a 3rd pipe that cycles the (cold) hot water line to keep it hot in the pipes. This seems quite wasteful and complex so I wouldn’t want to install that.

The thermostatic mixers can get as cheap as €25. Though I think the cheap ones have a degree of slippage, whereby mid-shower I have to increase temp. I don’t know if that’s because it lost track of my setting, or if I adjusted to the temp physiologically and need hotter water to psychologically feel the same level of heat.

What kind of bothers me about the pressure balance design is you cannot tell from the pics if it’s really pressure balanced. I think the one handle style goes back decades, and originally did not maintain a balance. You have a joystick of sorts but if the pressure on one pipe changes you don’t know if it internally balances to maintain the ratio. So you have to read the product description and trust it.

Yeah, kind of. I’m glad to hear they have that capability. But note that there are some non-thermostatic designs that come close to achieving the same effect. Those have a memory of sorts, where they know you want X volume of hot water and Y volume of cold water. Then if the pressure in one drops or increases, the valve will adjust the other line ensure the hot and cold have the same ratio regardless.

That’s pretty good. But it assumes the hot water and cold water are each at constant temps. So imagine if you get to near the end of a hot water tank supply, the hot water will gradually become colder. In that case, a thermostatic valve will open the hot even more to chase the temp you want. Whereas the pressure balance style will not. Perhaps more importantly, the pressure balance style does not counter the fact that the hot line will be initially cold since the hot water cooled down while sitting in the pipe. So you have to fiddle with readjustments until the hot pipe is maxed out.

You have two controls, 1 for temp and one for pressure (instead of the traditional hot and cold with independent pressure controls on each). The temp knob has a stop in one position as you turn it, which gives 38°C water. The cheaper models are external and use a wax cylinder inside:

Wax expands as it gets warm. So when you first add pressure, internally the hot water valve is 100% open. Then as the water gets hotter at the valve, it closes and starts letting cold water in to retain the temp you select. It reacts quite fast too, so even if you have screaming hot water arrive at the fixture it’s quick enough to protect you from scalding. You set it and forget it. If someone else in the house flushes a toilet or runs a washer or dishwasher, thus causing the cold water to lose pressure, the thermostatic fixture will automatically adjust to maintain the temp.

The pricier ones are internal, which means all the complex valves are buried in the wall. And instead of wax they use a bi-metallic mechanism (which exploits the fact that a couple diferent metals bend differently with temp, or something like that). They look like this:

I think that has 2 pressure knobs, one for rainfall and one for the wand.

Whole external kits with rainfall and wand start at €100. If you just want the mixer bar and wand, it can be as cheap as €25. The internal kits start at around €500. I like the external ones not just because they are cheaper, but the plumbing is simple. You just need to have hot and cold threaded ½" pipes sticking out of the wall 15cm apart, which the fixture can screw onto.

I appreciate the suggestion but that luxury option sounds way more complicated. Adding a thermostatic mixer under the sink needs no pump or electrical wiring, and does not need a third water pipe to go from the faucet back to the boiler. It’s just plumbing under the sink. And in my case, I happen to have spare thermostatic shower mixers so I would just be buying a couple fittings.

I would perhaps even sooner put a small electric tankless water heater under the sink, which would require just one water pipe rather than 3.

I think there’s even a compromise where an electric insti-heat gadget can be plugged into the hot water line to give instant hot water, which I assume shuts off when the hot water actually comes.

I’m afraid you misunderstood. The leak in all scenarios is in the same place - water enters a room two rooms over from the bathroom. It’s unclear whether it’s seeping in around the showerpan or walls.

That’s a different kind of leak. A leaky valve isn’t my issue. But indeed it is nice to have replaceable cartridges so when a valve goes bad it does not require digging up the wall and replumbing.

That’s hard to imagine. I would expect the plastic parts to withstand near boiling temps. The temp should drop some along the route. Often the the problem is people have their hot water tanks too low (to save energy), and then bacteria lives in the tank. So ideally the tank should be out of survivable range of most bacteria, and then showers should have a thermostatic mixer to prevent scalding. OTOH, if it’s a tankless boiler, you can probably get away with lower temps. So I would be tempted to conclude the cartridge you had was bad quality.

I don’t have anything specialized like simple green, but wouldn’t acetone or denatured alcohol make a decent primer? I think priming the smooth rubber surface should be the easy part but it’s the bitumen band that’s tricky. It has a sandy texture and sand crumbles off when I rub it. Perhaps I should steel brush it where it needs adhesive.

Thanks for the suggestion but in my case there is nothing to nail to. A shingle must be attached to thick (~2mm) rubber that’s just formed to be vertical. Perhaps I need to rivet the two rubber pieces together. Or I might try construction glue again but also get a couple metal plates and screws to clamp them together as a permanent clamp.

What’s the reasoning behind that ban?

The drain infrastructure in most US cities is relatively modern. The city drain pipes are big & thus able to handle a big amount of food waste coming from residents. I think I heard some minority of US cities also ban garbage disposals because for whatever reason their pipework can’t handle the load.

Old cities have small pipes that could not sustain the onslaught of thick food waste, as I understand it. In my city, rats outnumber humans by 2 to 1 and I think they thrive in the sewer. So I’m not sure if it’s also an effort to not feed rats. In any case, the city’s preferred way of dealing with waste food is to put it in the trash.

Recently they required food waste to be separated into a different color bag than the others. So they collect the food waste together and compost it. In the end, this is probably the most forward-thinking approach despite the sewer system being quite behind.

I can’t quite work out if you’re making a prediction of a clog returning, or if you’ve not realized that there is no longer a clog.

For weeks I have been fighting clog. But the clog is finally gone and the drain is now faster than I have ever seen. The drain actually keeps pace with the faucet on full blast. In the past, even in the best of times, I think the fastest it drained was 1 liter in 20 seconds. Now 1 liter drains in 6 seconds.

You’re already hundreds of dollars into gadgets and chemicals. Stop it. Cut your losses and call a professional next time.

Pros give different results in different areas. I called a plumber for a leak once. I was out of town, but a simple leak was dripping and forming a puddle on the floor. The leak was in exposed PEX pipe visibly strapped to the wall (yes that room is quite ugly). The plumber spent little time, failed to find the leak, blamed something that was fine, and charged €200. We called him back and he made the outrageous claim that the puddle was due to “condensation”. Left and gave no refund. I would love to have a reliable & trustworthy plumber. But since I don’t have that I have to become the plumber.

My costs in the drain fight were ~¾ of €200 (less than the incompetent plumber’s charge for simply showing up). Every time I redo the pipes I’m appalled by the work of past plumbers. So I think I’m just not in a good place to hire plumbers. There is no quality control of any kind in my area. No Better Business Bureau of sorts to record complaints. So the infrastructure is not setup for bad plumbers to fail.

Ok, so as you noted at the end, sulfuric acid was a bad idea for the pipes.

Not exactly. The sulfuric acid likely solved my problem (in combination with a plunger). It overflowed a little & attacked radiator pipes due to me underestimating the foam expansion rate (user error - perhaps poured too fast), but AFAIK it did not harm the drain pipes. Sulfuric acid would not be a good early stage choice, but when most chemicals and techniques have been exhausted it’s one of the most effective options.

The problem you will quickly run into is that you poored many chemicals in your pipe, so new chemicals might react with them.

That’s good general advice. But note that my episode spans many weeks. I know not to mix them (acid & bleach in particular). Every chemical went in on a different day with a water flush in between (which often took ½ day or a full day).

Bleach is not a dissolvant, it’s a disinfectant. It’s of no use to free a pipe.

I’m a bit confused on this because many of the consumer grade drain cleaners seem to rely on bleach as the active ingredient. Some of them are simply “thick bleach” (in a gel form).

To my limited knowledge, the best chemicals are acid chlorhydric or soda. Never ever use both. acid chlorhydric might be bad for the pipes though, so soda is usually better. Acid chlorhydric is best to remove limestone. Soda is best to remove biomater. Both of these are very cheap.

Do you mean hydrochloric acid & caustic soda (aka sodium hydroxide/NaOH)?

The hair-specific drain cleaner I have is based on sodium hydroxide.

The 2-component one was based on sodium hydroxide & sodium hypochlorite (aka bleach). I don’t recall what the other cleaners were.

Another point of confusion: chemists told me consumer drain cleaners are useless against hair. Then I noticed hair-specific drain cleaners on the shelf, which somewhat supports the idea that universal/generic drain cleaners lack effect on hair. But then the hair-specific drain cleaner I bought only mentions sodium hydroxide as an active ingredient, and this is the same common ingredient in many non-specific drain cleaners.