Plumbing Problem (Hot Water issue)

Factual Questions
1

I have a very curious problem with my hot water. My wife got up and took a shower, reported not having any problems. She left to run some errands. I got up, warmed the hot water while I brushed my teeth (normal routine, I let the hot water run in the sink while I brush my teeth so the shower will be hot when I turn it on; the water heater and the master bathroom are at opposite ends of the house so it takes a long time to get the hot water from the heater to the shower head). I turn the hot water on in the shower and it comes out to the tub just fine.

This is where it gets strange. When I turn the diverter to make it come out the shower head, the hot water stops to a trickle. I haven’t turned on the cold water, yet, and the hot faucet is on full. I turn the diverter to make it come out the tub and it remains a trickle.

At this point, I make the assumption there is something wrong with this bathroom and change plans. I go to the guest bathroom. Only a trickle for the hot water there, too. I check all the hot water faucets in the house and they all will just trickle. The cold water does just fine, but the hot water just trickles.

So, I take a trickle shower with as much cold water as I can stand. Not fun.

I don’t want to call a plumber because I suspect they will first just declare the water heater dead and replace it (a job I can do, and have done several times, myself), without finding out what the problem. Then, I’ll have to pay them again to come and determine what the problem is and fix that.

Now, I have looked at the water heater. The MFG date is 08/2005. It was installed in February 2006. I do not believe it is the problem, but maybe it is; it’s just I have not seen a water fail like this before.

Some might say, not unusual for a water heater to fail in 6 years, but our water is very soft (< 3mg calcium). The water heater it replaced appeared to be the original water for the house, built in 1976. If the first one lasted 30 years, I think 6 is a little short.

I though maybe the cut-off valve for the water to the water heater had failed, but it is a ball valve and it turns off and on just fine. I drained water out of both the pressure relief valve and the tank drain and they both get strong flow out of them. At all the faucets, though, just a trickle. It’s a gas heater and the heating part does just fine.

I’m stumped.

Excavating (for a mind).

2

What is the hot water pressure at the sinks? Just a trickle too?

3

Could you shut off the supply line and hook a garden hose up to the hot water side of the tank? (I think they’re the same thread size) That should tell you which side of the heater the trouble is on. Be careful though, the hot water side will be hot unless you’ve turned the gas off and left it off for a while. But if you do that, you might not have pressure problems once the water cools. That would be a clue too.

Just thinking out loud here.

4

hot water heaters live and die over the life span of the sacrificial rods in them. Some have larger rods or multiple rods to extend their life span. When the rods are eaten up, your water heater has no defense against corrosion.

5

Sounds like the hot output of your water heater is clogged with junk or corrosion. If you have good flow out the drain and overpressure, then probably the problem is not with the cold input lines. Assuming the heater fills up and heats during the night and provides one shower in the morning but not a second, it seems that it cannot heat and provide a second 25 gallons or whatever fast enough. Assuming that the cold is flowing well and knowing that it will heat at least one load, then you have a blocked heater coil or outlet pipe.

Turn off the cold in, let the pressure off and remove the hot flex line and look down the pipe. If the heater’s gone to hell, you’ll probably see that pipe corroded almost shut. If you’re lucky, you’ll find a screen washer/filter there that’s clogged with white junk.

6

Thanks for the replies.

I think I have it. I shut off the cold water to the heater then opened the hot water at the kitchen sink. That gave me the usual trickle, then it stopped (naturally). Then, I opened the tank drain, which started a small flow (kitchen hot was open). I closed the kitchen hot and the tank drain stopped. All as it should be. Then, I opened the kitchen hot and the kitchen cold and placed my hand over the kitchen outlet (where the water comes out, after I had removed the aerator). Pressure was high, spraying water all over the kitchen, then a “FLUGH” and there was very little pressure, but water started flowing through the pipes (I could hear it). My wife was watching the tank and she said the pipes shook and then water started pouring out of the drain. I shut off the valves, opened the cold water inlet to the water heater and all seems fine.

I guess I had something clogging up the line. Anyway, hot and cold run fine, now.

excavating (for a mind)

7

Problems that fix themselves return. The energy police have favored us with thingamabobbies on the inlet and outlet with little plastic flappers that can get stuck. Check what look like dielectric unions on your tank. Since I piped my tank up with plastic, I tossed them in my junk box without looking at them. I only later read about them.