Intermittent low hot water pressure?

Can't figure this one out. Sometimes the hot water pressure in our two showers is absolutely terrible, but sometimes it's great. It can be bad even with nothing else running (i.e. clothes washer or dishwasher). On city of Bryan water.

Any ideas? What do I need to start with?
something floating in front of the inlet or outlet in the tank is my guess...
Hmm. How would I go about attempting to clear that?
Turn off the valve into the HW heater. Hook a garden hose to the drain. Run hose outside. Drain HW tank. Open valve and refill.
I had a similar issue and never really figured out what caused it.

My hot water would totally stop. I could turn the faucet on and off, and nothing would come out. I figured there must have been some trash that got in the outlet of the water heater. At a sink, I turned on the hot water, put my hand over the faucet to stop it up, and turned on the cold water hoping to run the cold water backward into the heater. I'd hear a "pop" come from the water heater and the hot water would start running.

This went on for a few weeks and then went away. It hasn't done it in two years now.
I am willing to bet that the heater is FULL of rock if you have never drained it. It should be drained every 6 months, or at a minimum once a year...
Just tried to drain it. Couldn't get the inlet valve to shut (would only turn less than 1/8 turn). Didn't want to force it for fear of breaking it and requiring me to shut off the water and make a Lowe's run. I drained it anyway, and some dirty looking water came out, but still low pressure. I'm guessing it's hard to get all the junk out if there's still water flowing in? I may just go shut off the water at the meter and drain it again to bypass the valve issue.

I shut off the water at the meter and tried to drain it. In that situation, nothing comes out of the drain valve on the tank. I cannot figure out why. Any ideas?
yes, see my post above. Your heater is most likely full of mineral deposits and is toast. A new heater is most likely in order. The old one will be HEAVY, so get a dolly or some help to remove .

Drain your new one every six months...
tman - we just had a similar set of symptoms happen and had to replace our water heater. Our old one was 15 years old but just full of ****.
Well crap, otherwise this one works fine.

Would this be covered under a home warranty (Old Republic)? Since the pressure issue is intermittent, is the fact that it won't drain with the water shut off enough to demonstrate to them that it needs replacing?
When you do drain your water heater, be sure to turn the heating element off. Otherwise you'll crack the glass liner and be forced to buy a new one.

Would this be covered under a home warranty (Old Republic)?

Maybe. I am sure they are going to get you $50 as a deductible and don't expect them to volunteer to replace it. Home warranties are about the biggest rip off in the world, but maybe you will have some luck.

How old is the water heater?
yeah you probably should replace it, but if you don't want to you could add a valve on the existing drain. The valves they use in water heaters are cheap and often won't close especially if you have mineral buildup in it.
I would say it's either the inlet or exit pipe is plugged. Your cold water inlet is going to discharge near the bottom of the tank. If you turn the hot water on and don't fill at the bottom you will lose pressure in the tank. Likewise if you have corrosion at the top on the hot outlet you will get a high pressure loss due to the restriction. My guess is a rock pile over the cold water inlet.

If you only have loss in the two showers I would carefully pull the shower head off and flush it could have a restriction there but I don't see how it could be intermittent.

[This message has been edited by sunchaser (edited 12/8/2009 7:26p).]
It's full of calcium deposits, they look like sea monkeys.

Inlet valve to heater? There's nothing wrong with that. Cold water goes through that pipe before being heated. Shouldn't matter if you can shut it or not.

You need to use the drain valve on the bottom of hot water heater. It looks like outdoor spigot. Just hook up a garden hose and run it outside or to shower/sink. Then open that and watch the crap fly out of there.

You won't drain all the water. The stuff sinks so it'll be at the bottom of heater anyway. Just drain it until water looks relatively clear outside. Then watch a movie or game. Then try again. You'll get more gunk coming out. Do that a few times and it should work alright.
Right, what I'm saying is I tried to drain it, but only clear water comes out (and with lots of pressure). If I shut off the water supply, nothing comes out, even though I know the tank is full of water (since it's been sitting there for hours with no hot water use). Doesn't make sense to me, but hey, what do I know.
Did you open the pressure release valve at the top?
Don't mess with the pressure relief!

Think of it as a 55 gallon drum. Cold inlet on the outlet on the top. Drain on the bottom.

If you open the drain at the bottom hooked up to garden hose...inlet turned off you can expect 40 gallons to come out. If it doesn't come out the drain is plugged or you didn't have any water in your water heater.

If you can drain it....turn the drain valve the cold water should take a while to fill forty gallons....repeat. It's hard to imagine an old water heater with clear water coming thru the drain.

Do you have high pressure in the showers with cold water only?
With the inlet shut off (at the street since the valve on the heater inlet won't shut), no water comes out. None, nada.

With the inlet open, lots of clear water comes out. High pressure. When I first opened the drain, a very small amount of dirty water came out.
If you shut off the water supply, you will need to open a faucet somewhere to vent the system. Otherwise, nothing will come out. Or, shut the inlet and outlet valves, and disconnect one of the hoses to vent. Once it is drained, flush out the bottom by opening the supply valve. This should stir up any mineral deposits sitting in the bottom. While you have it drained you should also inspect the anode. This will be screwed into the top somewhere. If it is all gunked up replace it or you will eventually have stinky water.
And don't forget to turn off the gas while you are draining or you will be heating an empty tank.
Also, if the problem is only in the shower, take off the shower head and make sure you don't have any crap in there.
If you shut off the water supply, you will need to open a faucet somewhere to vent the system.

I tried that, no dice. Will try again today, or disconnect the hot water outlet to let it vent.

The pressure in the shower did seem a lot better today, so what I did yesterday may have helped. Pretty sure it's not just a gunked up shower head because 1) low pressure in two separate showers and 2) the pressure is low out of the bathtub spigot as well. But, it was better today, so we'll see.
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