I have to get up 20 minutes early and let the water run for a few minutes then wait the 20 minutes for hot water or else I will only get a lukewarm shower. The water only stays hot for about 7 minutes before it turns ice cold. What could be the cause of this?

Have you upped the thermostat on the hot water tank?

Twink, I don't think that upping the thermostat is going to fix his problem.

Dimoct, More details please. Gas norm electric heater? Did the shower ever work correctly?
Did this happen suddenly or come on gradually? How old is the heater? Do you flush your heater on a monthly maintenance schedule?
This could be a bad element if electric or a broken dip tube on either gas or electric. So let's start with you answering my questions. Regards, Tom

Is your shower the only fixture that takes this long to give hot water? If so you need the clean out the mixing valve, likely a cartridge

Hi Tom, I am renting renting and it has been a problem since I moved in 3 months ago. It is an electric heater that has been rebuilt. The shower never worked correctly and the heater was turned up a couple of months ago but did not fix the problem.

No the kitchen sink does too (Bob)
Yes and it did not help (Twinkie)

It's fairly normal to have to wait a minute or two to exhaust the cool water out of the lines before you get hot water. But it's not normal to have hot water 20 minutes later.
This could be a few things, It almost sounds like a broken dip tube but then again it could be a cross connection, either in a mixing valve or a faulty plumbing design. It doesn't sound like a bad element although I wouldn't bet on the top one. Do you wish to analyze this yourself or are you planing on calling in a plumber? Back to you, Tom

Hi Dimoct55

In my opinion, you need to call the landlord and let him know about this issue... have him fix this... not your problem!

In fact, if you or a plumber come in and "fix" this and break something I'm going to bet that the landlord will be crying how you shouldn't have touched things to begin with... ;)

At a minimum, call the owner and discuss this with him... cover your bases!

Good luck!

Mark