# Whats wrong with my question \[about hot water thermostats\]?? **URL:** \ **Category:** Factual Questions\ **Created:** [August 10, 2016, 8:44pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384 "2016-08-10T20:44:43Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 11, 2016, 2:50pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/21 "2016-08-11T14:50:26Z")
> [@Marvin\_the\_Martian](#): > > Where I live a check valve on the incoming water line has been required for decades, and is required to be installed in older houses when the house is sold. In fact, the rules recently changed to require a dual check valve instead of the old single flapper valve - I recently needed to upgrade the check valve since I am in the process of selling my house. > > The check valve is installed immediately after the water meter, which is far from the water heater in my house. Even if the OP installed and plumbed the water heater, there very well could be a check valve back at the water inlet. I will check that out, I don’t remember seeing one at the meter but I haven’t looked either. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [August 11, 2016, 6:25pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/22 "2016-08-11T18:25:23Z")
You said all 3 gave you the same answer. Odds are they were right. But … What answer did they give you? ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 11, 2016, 7:49pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/23 "2016-08-11T19:49:20Z")
> [@Boyo\_Jim](#): > > You said all 3 gave you the same answer. Odds are they were right. But … > What answer did they give you? That was in my original post, they expalined it had a safety valve which I already knew about. I just checked it a little closer and the termostat spring is not acting right. It cuts off and on if I turn it up a bit higher but the space between the cut on and cut off has grown my wider. Way too much play in the spring. I am going to see if I can take it apart and if it is not broken I might be able to lube it. ---
**Author:** ![CannyDan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cannydan/32/548_2.png) [@CannyDan](https://boards.straightdope.com/u/CannyDan)\ **Post date:** [August 11, 2016, 8:24pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/24 "2016-08-11T20:24:55Z")
Is there a reason you don’t just replace the thermostat? The ones I know aren’t too expensive, and the amount of checking and poking around you’ve done and are going to do probably exceeds the time needed to R&R the unit. Certainly it is within your skill level, since you set up the entire system. I’m not criticizing, I’m just curious. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 11, 2016, 10:15pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/25 "2016-08-11T22:15:36Z")
> [@CannyDan](#): > > Is there a reason you don’t just replace the thermostat? The ones I know aren’t too expensive, and the amount of checking and poking around you’ve done and are going to do probably exceeds the time needed to R&R the unit. Certainly it is within your skill level, since you set up the entire system. > > I’m not criticizing, I’m just curious. I am going to put in a tankless water heater when I get back from vacation but don’t really have time to do it right now unless I have no choice. The new thermostat costs more than 1/2 of what a new heater would cost. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [August 11, 2016, 11:04pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/26 "2016-08-11T23:04:28Z")
You are giving way too much conjecture in your question. I learned this a long time ago with car mechanics. If you tell them that you think the clutch has gone, they are likely to replace the clutch. If you say that pressing the pedal has no effect, they may check and discover that the cable came off the connector at the pedal. You should keep it simple, state the problem and ask if they have any idea why. \*“The hot water stays at 120 even though I set it at 102. Have you any idea why that might happen?” \* The answer is almost certainly, as determined above, a faulty thermostat. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 11, 2016, 11:15pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/27 "2016-08-11T23:15:51Z")
> [@bob\_2](#): > > You are giving way too much conjecture in your question. I learned this a long time ago with car mechanics. If you tell them that you think the clutch has gone, they are likely to replace the clutch. If you say that pressing the pedal has no effect, they may check and discover that the cable came off the connector at the pedal. You should keep it simple, state the problem and ask if they have any idea why. > > \*“The hot water stays at 120 even though I set it at 102. Have you any idea why that might happen?” > \* > The answer is almost certainly, as determined above, a faulty thermostat. Because I knew what the problem was from the beginning, it was never an issue what the problem was. The question was whether or not their was a secondary thermostat that would keep it from over heating, like a safety over ride. That was my only question. I already knew the fix. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 11, 2016, 11:25pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/28 "2016-08-11T23:25:48Z")
I spent my entire life as a diesel mechanic and I just feel better when I understand something even if I have no real use for the information. That was the main reason I was asking. My question here was not about my thermostat either, the question here was about my question in case you didn’t pick up on that. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [August 13, 2016, 1:37pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/29 "2016-08-13T13:37:51Z")
> [@HoneyBadgerDC](#): > > The question was whether or not their was a secondary thermostat that would keep it from over heating, like a safety over ride. The answer is maybe… I think when your thermostat dial broke, its just running at the maximum the dial can be set to , 120F. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [August 13, 2016, 1:51pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384/30 "2016-08-13T13:51:23Z")
> [@HoneyBadgerDC](#): > > Because I knew what the problem was from the beginning, it was never an issue what the problem was. The question was whether or not their was a secondary thermostat that would keep it from over heating, like a safety over ride. That was my only question. I already knew the fix. Sorry - I misunderstood. I think that the idea of a second thermostat was so unlikely that they just talked about the secondary safety system that would be fitted. ie. The pressure valve. [Previous page](https://boards.straightdope.com/t/whats-wrong-with-my-question-about-hot-water-thermostats/762384.md?page=1)