Ah, plumbing!

 Four years ago, in the early days of the pandemic, when everything was locked down, our hot water service broke.

We had planned on a greener replacement, but in the middle of the pandemic, we ended up with a like for like replacement.

And it's been fine, delivering hot water when we want it.

Now, like many Australian houses we have tempered water in the bathrooms - basically cold water is blended automagically with the hot to ensure that you can never accidentally scald yourself in the bath, or at least not as badly if you used water straight from the hot water tank, which sits somewhere between 65 and 70C.

Our kitchen and laundry/utility area both get proper hot water direct from the tank - when we had the kitchen renovated the plumber doing the work asked us if we wanted 'proper' hot water or tempered water in the kitchen. 

Not really understanding what tempered water was we went for 'proper' hot water, especially as we don't have young children around.

The automagical blending is done via a tempering valve, which at its simplest consists of a bimetallic strip opening and closing the hot water line as required

This is a picture of our old one, and probably about twenty five years old.

At some point in the last few months, ours must have ceased to do its magic and stuck part way open.

We don't know when it failed, as over summer our cold water is never really cold, more tepid or cool, and the valve must have been letting in enough hot water that we still seemed to be able to have hot showers in the morning.

Well, over the last few days it's turned to a classic Alpine autumn, clear sunny days and cold starlit nights and our cold water has turned properly cold again.

Unfortunately so did our shower, which went from acceptably warm to lukewarm.

At first I thought that the thermostat on the hot water system must have gone.

So I called a local electrician who came and tested it - no it was working fine, as was the heating element. However he flipped the tank bleed valve and was rewarded with a jet of 70C water.

So it wasn't the hot water system. He guessed it might be the tempering valve and suggested that I call a plumber.

Swapping the valve solved the problem, hot showers all round. The plumber also showed me how to adjust the degree of mixing and hence the temperature of the tempered water - incredibly simple if you know how, you just need the right tool, a little triangular valve key.

So, lesson learned. It isn't always the hot water thermostat. 

If the hot water in the kitchen sink is noticeably hotter than the shower, you probably have one of these automagical valves on the bathroom supply, and if it goes wrong, as ours did, you should find that the sink hot water should stay hot while the shower gets progressively cooler ...