What the ... heck!

[Tom the Elder]

Finally got around to draining my new 29-gal Rheem gas water heater - now 16 months old (located on back porch). Turned it off last night. Today attached hose to drain valve, shut off cold water, opened drain valve, and opened shower hot valve. When I opened the shower valve I could hear air sucking in. Went back to the porch - no water coming from hose. Double checked drain valve was fully open and could feel the hose beyond the valve was warm to the touch. Considered a possible blockage in this old hose so blew into the end and could hear bubbles in the tank - but still now water coming out (end of hose about 2 ft below drain valve). Opened the cold water valve and water gushed from the tank - but when I shut it again the water stopped completely.

My house is 70 years old so I can't imagine there is any kind of backflow preventer in the system and I certainly did not install one in the 30 years I have been here (yep, first water tank flush in 30 years). I could open the pressure relief valve but I seem to recall those can fail easily if used much - and I hope to regularly flush this tank. My plan was to drain the tank and replace the drain valve with a full-port ball valve to make flushing more efficient but the damn tank won't drain! At this point the only other thing I can think of is to call in an exorcist. Anybody have a better idea?

 

[Jeff Handy]

Just leave the cold inlet open.

Close the shower valve.

It flushes better that way anyway.

The incoming water stirs up the settled crud.

 

[breplum]

That drain valve is utter garbage.
Remove, replace with a quarter turn full port lever handle ball valve, and add a threaded hose adapter to the outlet, then cap the hose outlet or remove the handle, to prevent inadvertent issues.

 

[Twowaxhack]

Leave it alone......cap the old drain valve with a brass garden thread cap.

Or replace the water heater.

 

[Duckbutter]

Jeff Handy's right, flushing is better with pressure/turbulence anyway, that said.

After just 16 months you really shouldn't have that much debris, My guess is the hot pipe is trapped, dips down and back up before the shower just enough to prevent the start of syphon OR the shower valve's pressure balancing is the problem, you'll likely have luck with a small pump, or try opening other hot faucets.

HD/Lowes sell tiny pumps you can connect to a cordless drill, perfect for this.

 

[JG plumbing]

You don't really need to drain the entire thing anyway.

 

[Tom the Elder]

Jeff Handy, I agree flushing under pressure a good idea, but I want to replace the drain valve with a full-port ball valve to maximize water flow.

 

[Tom the Elder]

Breplum, that was exactly my plan – but have to be able to drain tank to replace valve.

 

[Tom the Elder]

Twowaxhack, replace 16 month old water heater? I don’t think so.

 

[Tom the Elder]

Duckbutter, opening multiple taps is a great idea. My area has very hard water so I plan to flush annually. TINY PUMP! Fantastic! I had never heard of that and almost hope opening multiple taps does not work so I have an excuse to buy one!

 

[JG plumbing]

Breplum, that was exactly my plan – but have to be able to drain tank to replace valve.

No you don't. Just take the valve off and replace it. You yourself said it's airlocked. Even if it wasn't airlocked you can replace the valve.

 

[Tom the Elder]

JG, I do need to drain it if I am going to replace the drain valve.

 

[Twowaxhack]

Twowaxhack, replace 16 month old water heater? I don’t think so.

Yeah, I misread it as 16 years old.

When you open the drain you need to give the heater air to drain through the relief valve.

If the relief valve fails to close, replace the relief valve.

 

[JG plumbing]

JG, I do need to drain it if I am going to replace the drain valve.

You don't. I did mine two years ago. I taped it and doped it and spun it in,while it glugged. There it sits now, with a new full port ball valve.

 

[Twowaxhack]

Duckbutter, opening multiple taps is a great idea. My area has very hard water so I plan to flush annually. TINY PUMP! Fantastic! I had never heard of that and almost hope opening multiple taps does not work so I have an excuse to buy one!

There’s a hole in the dip tube to prevent a water heater from siphoning more than a few inches down from the top.

Opening multiple faucets won’t help.

A drill pump is not needed, just give the heater a little air through the relief. This is a good time to check it’s operation since you wish to maintain it as the manufacture intended.

If you want to flush with a little pressure, go ahead. Just open the drain while the waters on.

 

[Twowaxhack]

You don't. I did mine two years ago. I taped it and doped it and spun it in,while it glugged. There it sits now, with a new full port ball valve.

What heater did you buy that came with a plastic valve ? Box store ? Or was it brass but not full port ?

All important questions ......

 

[JG plumbing]

What heater did you buy that came with a plastic valve ? Box store ? Or was it brass but not full port ?

All important questions ......

It was there when I got there

 

[Twowaxhack]

It was there when I got there

Welll..........what brand is it ?

 

[JG plumbing]

Welll..........what brand is it ?

I'll look when I get home. Rheem I think.

 

[JG plumbing]

Looks as though it's a Rheem. The other valve is on top of the heater. Now I remember it had a brass valve with a flat head as the handle that wouldn't open worth an f. Since inquiring mind wants to know.