Trying to figure out how to diagnose the master shower in a 26 year old house. It takes an extreme amount of time to get hot water. The other shower (in next room) and all of the sinks all get hot water quickly. I finally bought a temperature sensor led shower head so I could tell when to bother to get undressed, but it is wasting five minutes of water while I wait. Could it be the control (MIXET) causing this ? Or?

It could be number of things... Before you do anything, I suggest you remove your shower head and run shower w/o the head installed. See how fast you get hot water now... Let me know what happened... Back to you... Milo

Did this shower always take a long time to get hot or did it just start? Back to you, Tom

It takes about 3 minutes without any shower head. We have been in this house 1 year. Been a problem the whole time. Changing shower heads hasn't affected it much. It will take longer as weather gets colder

This sounds like a design flaw. Does this also affect the bathroom sink? Have you considered adding a recirculating line to the bathroom? Would you like to learn more? Cheers, Tom

Bought a recirculating pump but returned it when I realized master shower is so close (>10 ft) to other shower and 3 sinks (for some reason 2 in guest bath and 1 in master). Master Bath sink doesn't seem to take as long.

Remove the shower head on this bad shower and the other one. Set both to the hotest setting and turn them both on collecting in a bucket. Did they both produce the same volume of water and was the temp the same. This could be a clogged hot supply inlet or faulty mixing valve.

I will have to try that in a few days, I only have one bucket. I would be surprised if line is clogged. The new showerhead needs cleaning already- it's showing signs of clogging and screen had stuff in it too.

A mixing valve or shower head can plug almost instantly upon installation if there is debris in the line which gets knocked loose when the main is turned back on.

Above posts are correct... You will have to investigate why all other bathrooms are getting enough hot water and that shower is not. As mentioned, it may be a design flaw, kinked pipe, partially closed valve / angle stop, kinked pipe... and more.

Is this bathroom a new addition ?
Do you have crawl space or are you on slab ?
Do you have PEX pipes installed ?
What kind/type/brand of faucet is in that shower ?

Back to you... Milo