Tepid water

[TribesTime]

Need expert plumbing advice please

I have a 5 year old Richmond/Rheem natural gas 50 gallon hot water heater.
It has been performing fine till recently.

A few months ago we started running out of hot water during a 2nd person showering. So maybe after 13 - 15 minutes. Then it got worse and lasting only 8-10 minutes of hot water before going tepid to cold.

I drained off a few gallons a month ago; noticed a little blackish color in first "quart or so", but then clear. Funny thing though, it came out at a trickle, could barely get a good draining in my opinion. Flame through the window looks fine/perfect. Cranked up the temp just 1 notch, too.

Seemed to help for a while and 2 showers did fine.

Now back to tepid after only about 8 minutes of showering with no other draw. After about 5-7 we even turn cold to almost off and still it isn't burning water and I have the thing cranked up to about 135 degrees setting.
First coming out of tub faucet when starting and the water is indeed burning hot.

Thoughts? Thermocouple seems fine as flame seems fine.
What do I check?

 

[stevemachine]

Probably a dip tube, or sediment in bottom of the water heater. If its hot then goes cold after a bit I'd say dip tube. Dip tube brings cold water to the bottom, since cold water is more dense it stays at the bottom and once its heated it rises. If the dip tube is shot the cold water will end up at the top and end up going to your open faucet instead of being brought to the bottom.

 

[TribesTime]

That might make sense - I'll check that - appears I need to drain & pull cold supply (let me know if that's wrong way to service that). Any thoughts on getting better drain than a trickle?

 

[stevemachine]

Yes drain the tank a bit and that cold nipple sticking out of the tank has a plastic tube on it, there should be roughly 30 ish inches of plastic on the end of the nipple. So yeah pull it out, make sure you have Teflon tape and preferentially dope as well so when ya install the new one it'll be good to go. I believe rheem has one specific to their tanks so make sure you grab the right dip tibe. For the drain what I've done and sometimes works is drain the tank for a bit, even if it trickles, and turn the water on fairly fast and it should stir some sediment up and hopefully drain it out. I'd fix the dip tube first, if you fix that then it'll reach the bottom of the tank and it'll stir the sediment up more to get it to drain better. Usually what'll happen is sediment builds up, settles at the bottom and then blocks off the drain port basically so all you get is a trickle. Also while your at it if you have a plastic drain/sediment faucet you may want to replace it with a brass one, I've had tons of those leak on me. They're junk. Another thing you could do is if it has a separate anode rod, pull it out and replace it as well. 1 1/16 socket i believe to replace the anode rod. If you replace all this it'll be like 50-60 bucks in parts and you'll practically have a new water heater. You could also trip your relief valve and make sure it works, if it drips afterwards then you'll need to replace it. These are just optional but things to consider. Usually water heaters that aren't maintained properly will last 10 yrs roughly now a days. If ya replace anodes regularly like every 5-6 years it'll probably double its life.