My shower starts hot for about 2 - 3 minutes then starts turing cold. Hot water in bathroom sink is still hot when I check it out after shower goes cold. It's a Delta faucet with separate control for temperature and I believe it is an anti-scauld faucet Our water heater is a Ranai tankless.

Hello rddelong, question: if you leave that shower ON for bit longer, does the hot water returns ?

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Milo