They make use of the TP valve outlet which is close to the hot water outlet.
Combining the TP valve with the hot water return was a plumbing challenge!
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Thanks. That explains it perfectly well.
And I do.
Vertical geysers are perfect for a quick shower, and with timer use, as it heats less water.
AND they get quite quickly on temp for a quick shower.
BUT … big BUT … cause you can have a nice temp starting the shower if you don’t “focus”, whilst showering, the temp can fall off a cliff. The wife said so. I ran.
Flip side … on a timer, being heated from the top to the bottom, to where the element switches off … now that is a LOT of hot water.
Just need to focus a wee bit. Learn the quirks of vertically mounted.
I bought our house already fitted with a SWH (flat plate) and I can concur in Summer it works very very well, but every year in winter when I see our consumption swing so wildly I get the urge to install a heatpump, and I know by October the idea will be out of my head again, only to reemerge in June the next year 
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… and my suspicion is something is wrong with the diverter valve, since it basically just dumps the partially heated water into the top of the tank. I’ve also been told not to mess with the diverter valve, because you can easily make it worse.
Since I’m a curious fellow, one way might be to just buy a cheap diverter valve, play with it a bit, and when I understand it… then make some kind of a plan. Or pay someone to fix it, but I have this internal resistance to doing that, because I hate not understanding the real problem.
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Read this on another forum … man, it is so well said!
The other day I paid someone to come fix a gas leak. Of the LPG kind. We could smell it, but no amount of soapy water could find the darn thing.
Winelands gas charged me a call-out fee, which was like 6 or 7 expensive coffees, I paid it and their guy showed up. Asked me for a lighter. Much to my consternation he set fire to the leaky pipe, then blew the flame out, and tightened the connections down some more (they were already tight after I was in there).
It had finally gotten bad enough (a 19kg bottle emptied in a week!) that I decided to call someone.
But, last month I also spent a 5-digit number on fixing a leaky shower (because the idiots who built it put down absolutely zero waterproofing). And cash flow is also a thing. Less serious stuff… must maar wait…
Hmmmmmm…
Not sure if it’s exactly the same, but I know that with my ITS heat pump I just have the timer set so that it is heated up before using it, otherwise it just starts pumping the cold water out the bottom, partially heats it up and adds it to the top causing the whole geyser temperature to drop before properly starting to heat up.
I always thought it’s ‘expected’, but this sounds like maybe there is more to it and maybe the diverter valve isn’t set correctly. I remember specifically asking about the diverter valve’s setting when they were busy with the installation and I was also told that they leave it as it comes out of the box as it’s set correctly, but after reading this it makes me think otherwise.
I have an issue with my anti-siphon loop though (it doesn’t work and drains the geyser when there’s water issues in the area), so it may be that it maybe causes water from the bottom to be taken where the diverter valve should be doing it’s think, but I know less than nothing and without getting the anti-siphon loop fixed I won’t know if it’s that, but I’m guessing it’s not that.
I got caught out like that yesterday. Had the geyser all nice and heated up, the missus had a shower, but I got caught up with work and only went for a shower at 14:15, after the heat pump starts up at 14:00 for its afternoon heatup, only to have a lukewarm shower as the cold water from the missus’ shower was now mixed through.
I also used to have a 09:30 - 10:00 timer before the pool pump starts to just heat up enough for the little bit of hot water needed before 14:00 for dishes etc., but also switched it off as it only brings down the temperature of the whole geyser.
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It is ‘expected’, in the sense that this is what heat pumps do if you don’t intervene in some way. But it is not expected, because the diverter valve is supposed to ensure that it doesn’t.
Anyway, it is one of those things that I deal with every winter, and by September I’ve forgotten that it needs attention.
The plumber that installed my system explained to me the diverter he installed traps the water in the heatpump and once it reaches a certain temperature (you cannot change this temperature) it releases the water to the geyser. In such a system, ITS limits the temperature for the water to 53 degrees (it goes to 55 degrees if you don’t have this valve based system). I’ve not had any issues with this. The temperature the valve opens up is something like 45 degrees (can’t remember exactly what the plumber said) and this basically means that if I don’t run the heatpump until it stops based on temperature, the top water in the geyser will be colder than the usual 53-60 (ITS mentions that the 53 degrees at the bottom setting means the water at the top is over 55). So basically just run it until it completes its job. And don’t make it come on while showering, because then it will be say 45, not 55 (which the wife likes to burn herself with).
Ugh. Well, now I’m just annoyed.
The manual specifically says this:
The heat pump will first re-circulate water through itself via the loading valve till the outlet water is more or less 50°C. At this stage the loading valve will start to open and the hot water will start to move towards the geyser.
and
The ITS loading technique is ensuring that hot water will be available within minutes from switching on.
I went to take a look at mine and the diverter valve doesn’t even have the knob to make adjustments, so even if I wanted to I can’t.
The documentation on the valve I have makes it sound simple enough:
Increasing the maximum temperature:
Turn the knob anticlockwise to (+). Loosen the screw and move the knob out to the side. Then turn the knob clockwise to (-) without it being engaged. Adjustments are carried out in small steps. A ¼ turn corresponds to approximately 7 °C. Reinstall the knob and check that it engages with the teeth. Tighten the screw and then turn the knob to max (+). Max. calibration for increasing the temperature is a ½ turn.
My loading valve (yes, that is the word I was looking for) is not one that I can set the temperature. It is an analog thing, probably working with some type of metal/wax that melts at a certain heat and then solidifies again once colder water cools it down… I’m guessing.
It has a bi-metal spring similar to thermostat used in a car. It is similar to a tempering valve (which lets cold water in to bring the temperature down).
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I asked Kwikot about the distribution of heat in a geyser and I received this memo from their technical head honcho:
“Hi Guys
The water will behave in a thermal cylce when the element is on – as soon as it switches off the water stratifies into layers with the hottest on top. The thermostat will then switch on again until this process has evenly distributed the stratification.
If you feel the inlet pipe of a geyser that has been on temperature for some time you see that it is hot.
At least 80% of the water will be at the thermostat setpoint after say 6 hours.”
So whilst the immersed element is on it will produce a ‘thermal cycle’ which will create more even heat distribution. This I presume is due to its position in the geyser.
And feeding hot water into the top of the geyser will not produce this effect…
I guess that’s also the beauty of putting a system together by oneself. The valve I got has an adjustment. Two weeks ago when I was in the roof, I realized that the water was getting too hot before going to the geyser and as a result, the bottom of the geyser wasn’t gettting hot since my sensor is not a the bottom. So I ran the heatpump and turned the diverter valve setting and I could then hear the water flowing to the geyser a lot easier.
Seems like the spring tension gets adjusted when I turned the screw on the valve. The valves a relatively cheap. Was about R600 3 years ago.
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Can you hear this without listening with a screwdriver on the pipe and the handle in your ear??
Yes. No metal rod needed but I was crouched about 20cm away from the pipe.
This indeed is what happens.
The standard temperature sensor at the centre of my horizontal geyser doesn’t budge even though hot water is flowing into the top. Finally when it does it rises fairly quickly and the water reaches setpoint and the heating cycle is complete.
I’ve written the installation date on mine but how long do they last?? 
That depends on your water hardness. Some insurers demand replacement every 2 years, which is basically the lower limit - the safest approach.
The lazy way to find out is wait for the geyser to start leaking/burst. Subtract one year from that and replace your new geyser anode then.
My previous anode lasted just over 5 years, but my replacement geyser has 2 of the same anodes. This obviously invalidates my previous test, so now I have to wait for it to fail again…