Was running out of hot water before even drawing a full bath whenever no hot water was run for 6-7 hours prior. Got a JMan plumber replace dip tube. When that didn't help, replaced the entire tank with a gas-heated 50-gallon one. Still having the same problem. He already inspected for any possible cross-connections and ruled it out. Help!

Hi Luthien and welcome, does the heaters burner stay on? Did your plumber rule out a leak? Does the pipes run under a slab or maybe from the pump house underground?

Hang tight maybe someone else will come up with something better. Good luck

OK! Here's another one. It's far out and won't reflect too well on the plumber but if the hot and cold were reversed on installation that would give you exactly what you're experiencing,
Is there a recirculating system installed? How did the old dip tube look? Back to you, Tom

I'm doubting that a new heater would be installed backwards, but it has certainly happened before, so I'd double check that as Tom suggested, for sure!

With that being said, I'm going to bet that the water heater or the dip tube never was the real issue. Instead, I'm betting that you have a single lever faucet that has a cross connection or has simply failed and is allowing cold water into the hot water side of the faucet and it is overwhelming your hot water delivery... ;) You could also have a two handle faucet that is connected together, such as at the washing machine water supply, and that could cause your issue, too!

If you'd like to discuss how to find which faucet is at fault let me know and we can discuss the next steps to take, OK?

Mark

PS: Curious, when the plumber removed the dip tube, was it defective or in perfect condition? Plumber should have not replaced it if it was good!