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sandstone
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Posted: Sat Aug 2nd, 2008 05:25 pm |
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| Hello, I have a ~25 yr old (must be the good Chicago city water) 40 gal Rheem Fury gas HWH with no recirc loop. We've been in the house for 13 yrs and we noticed in the last few years that the shower temp cycles every few minutes from whatever the desired setting is to hot enough to make me move out of the way. We originally attributed this to the kids flushing the toilets while we were in the shower but just realized that flushing is not the cause since it happens when the only person in the house is in the shower (flushing just makes it worse in this old 1923 house). I did the cross connection test and got no flow but, before I turned the supply to the HWH back on, I left a sink hot water tap open, opened/pulled out the shower valve and rotated it from hot to cold and got cold water to come out of the tap on the sink. I didn't have to rotate the knob much to get flow. Is that normal? I'm thinking that this is a deadband issue but the 1st shower in the am always varies from hot to too hot. We almost never run out of hot water even when doing a load of laundry and taking 1-2 showers back to back so I'm reluctant to change out the HWH since it isn't leaking. I think the shower valve is a Moen. The tank gets drained with zero sediment and RV tested yearly and the anode has never been changed. I've tried to pull the anode but I'm afraid I'll break the head off. I'm not sure what condition the dip tube is in since the tank is hard piped and I'll have to cut the line to pull it. Sorry for the long post but thanks in advance for your assistance.
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eleent
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Posted: Sun Aug 3rd, 2008 09:21 pm |
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Hello: There are different things that could be causing the overly hot water. I'd check at any hot faucet/s when you get hot or too hot water at the shower, to see if you get the same temperature at other fixtures. If the shower is not in line with what other fixtures are delivering, the shower rather than the heater is at fault.
How about doing those tests and letting us know what you find?
Yours, Larry
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sandstone
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Posted: Mon Aug 4th, 2008 12:23 am |
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Kinda hard to monitor a faucet and the shower at the same time beacause my wife likes to shower so hot that she showers alone  but here's some extra info. I used the 1st floor shower without the same problem. The one with the problem is on the 2nd fl. Both showers have low flow heads but I haven't used the 1st fl one in probably 12 years. I also took some temperature readings in the basement laundry with a digital pyrometer. Readings are at 3pgm and are as follows.:
Time (min), Temp (F)
0, 122.8
5, 122.6
9, 122.0
10, 114.2
11, 104.0
12, 100.4
15, 97.2
T=0 is when the hot water came up to temp. The temp never cycled but stayed steady until about 30 gals were used and then dropped slowly until I stopped the test. I haven't showered with my pyrometer but after 5 mins or so the water temp gets hot every min for about 10 secs. Bad shower valve? It looks like the attached.
Attachment: shower.jpg (Downloaded 37 times) Last edited on Mon Aug 4th, 2008 12:24 am by sandstone
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eleent
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Posted: Mon Aug 4th, 2008 06:20 am |
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Hello: Various thoughts. Anyone with a digital pyrometer probably has a pressure gauge in their back pocket  I'd use a 0 to 160 or 200 psi gauge with a hose thread attachment and simply watch the line pressure for a bit to see if it jumps around. If it does, that could be the cause of the fluctuations. If the Moen shower valve is one of the newer pressure balanced valves, might the shuttle inside be sticking? This is not exactly a problem I've had with this valve, but a call to tech support might be useful (1-800-289-6636) is the general number. A further confirmation for narrowing down the problem might be your checking a lav faucet in the bath while the shower is being used. Somehow you and the bather need to communicate any temp changes and confirm by checking the faucet. If the faucet stays even, you know it must be the shower valve. You get to work out the details of loitering in the bath 
Yours, Larry
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sandstone
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Posted: Sun Aug 10th, 2008 09:59 pm |
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| The pressure was fairly steady at 45 psi. However the hot faucet in the 2nd fl bath was steady while the shower cycled from normal to about 10F higher. The bathroom was done by the previous owner in ~90 so I wouldn't think that the shower valve would be anything other than simple a mixing valve...guess not. Thanks for your help. I'll order a flex combo rod for my old HWH from you guys since I haven't been able to get that hex rod out. Last edited on Mon Aug 11th, 2008 12:56 am by sandstone
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eleent
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Posted: Mon Aug 11th, 2008 12:23 am |
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Hello: It might not do any good, but this looks like Moen and that cartridge is not usually hard to replace. So, replace it with the polysulfone plastic unit rather than the brass one and see if that helps. It's just a hunch, but there isn't much else you can play with here. Do let us know if it has an effect
Yours, Larry
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sandstone
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Posted: Sat Aug 16th, 2008 12:18 pm |
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| I changed the cartridge. It's a simple mixing valve that uses a Moen 1225/12801 replacement but it didn't correct the problem. The old valve was probably nylon or acetal and the new one was clear polysullfone. Other than some weird pressure cycling on the hot or cold side only I can't for the life of me figure out what's going on but I must after all I'm an engineer and nothing goes unsolved!
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eleent
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Posted: Sun Aug 17th, 2008 05:25 am |
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Hello: Sometimes if we don't know what it is, we ask what it isn't. You pretty well know it is not the water heater. You wouldn't get even temps to any faucet if the heater were misbehaving. It is not the actual shower valve. That leaves only the plumbing around the shower, as other plumbing seems to work. You're not finding pressure fluctuations. If hot water somehow made it's way into the cold line, it would upset the mix of hot and cold and you would get Hot water as you are. I don't see that we've talked about cross connections. Turn off the cold supply to your heater and then open a hot tap. Water should flow for a few seconds and then stop. If it keeps running, there is a cross connection. See if you have any other Moen faucets. They sometimes do this with the brass cartridge. Let us know 
Yours, Larry
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sandstone
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Posted: Sun Aug 17th, 2008 02:52 pm |
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| In my first post I wrote, "I did the cross connection test and got no flow but, before I turned the supply to the HWH back on, I left a sink hot water tap open, opened/pulled out the shower valve and rotated it from hot to cold and got cold water to come out of the tap on the sink. I didn't have to rotate the knob much to get flow. Is that normal?" I don't have any other Moen valves. All other sink and shower valves are two handle except the kitchen sink.
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eleent
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Posted: Mon Aug 18th, 2008 02:38 am |
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Hello: My brain must be wearing out  I imagine water ran from the one tap when you opened the other only because air could get in and allow the pipes to drain, or cool water had an opportunity to run to lower pressure. I have heard of the rare casting defect in shower valves, but that's a stretch. Using wild imagination now, if you had a very low flow shower head, possibly water could move from hot to cold while the shower valve was on. But, that too is a stretch. It would be just as easy to believe that you opened up the wall and a gremlin jumped out, gave you a mischievous look and ran off... allowing the plumbing to work perfectly. Being the engineering sort, I'm more inclined to think I'm missing a piece of info. But, please let us know what it really is when it shows itself!
Yours, Larry
ps. If there is a way to feel both hot and cold shower lines while the shower is being used, (from under the house?) you could tell if the cold side warmed periodically. This would confirm hot getting into the cold side.
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sandstone
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Posted: Wed Aug 20th, 2008 01:08 pm |
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Well since the shower valve is just a mixing valve, now that you mention it, it makes perfect sense that cold water ran from the one open hot tap when I opened the shower because the cold water ran to lower pressure.
BUT... drum roll please... I found the problem  . Thinking about weird pressure fluctuations and just having replaced a leaky toilet valve in the basement, I valved out the toilet next to the offending shower, took my shower and guess what? Very minimal temperature fluctuation all the way through the shower. I checked the flapper and it's leaking very slightly. I replaced the flapper which is still leaking(flapper seat is ok) unless I push down on the flapper so I'll correct the toilet leak and put this nuisance behind me.
Since the toilet is teeing off from the shower line the flapper leak was partially tripping the toilet valve every minute for about 10 secs to refill the toilet. This would happen only when the shower was on since there was enough line pressure to the toilet with the shower off to keep the toilet full and only create a small "hissing" flow through the toilet valve. I didn't notice this because the vent fan is always on when the light is on in the bathroom and even with the light off the leak was very hard to hear. Now this is two years of trouble-shooting. Thanks Larry!!!
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