Hot water not as hot lately?

Do you kind of feel like your hot water isn't as hot lately? Or that you'e having to move the dial closer to the hot position than you did a month ago to get a nice hot shower?
Well, you're right. The reason is that the incoming cold water is colder now than it was a few weeks ago. So, when you used to mix 25% cold water to your 75% hot water in the shower, that now-colder 25% is overwhelming the 75%. Now you've got to add more hot and reduce the cold mixture to meet the same target temperature. Add to this, the hot water tank is working harder to make up for the colder water it's taking in as you draw from the hot water faucets. 
Wouldn't it be nice if you could figure out a practical way to preheat the incoming cold water before it goes in to your hot water heater? 
Discuss?


I'm surprised the latest and greatest technology has not yet gotten to water heaters.

A user settable thermostat hooked up to a probe, such as the laser pointer probes used to get temperatures may work. The thermal probe would relay temperature to the water heater's thermostat which would then then turn on the heat if needed.

My question is why wouldn't the water heater keep the water at a constant temperature? There must be some kind of temperature probe or else how would the heater know when to start heating the water? And doesn't it stop heating when the water reaches the desired temperature? Wouldn't extra cold water added to the tank just get the heater started quicker and then heat longer to get to the desired temperature?

Maybe the only basic change desired would be a thermostat so we can set with temperature instead of using the simple dial.


BG9 said:
My question is why wouldn't the water heater keep the water at a constant temperature? 

 Yes, but the water coming out of your shower head is not only coming from the water heater.  Your shower control / valve mixes water from the tank with cold water from the street.  So if the cold water from the street was colder than it was in August, you have to use more hot water to reach the temperature you want at the shower head.  So not only are you using more fuel to heat the water in the tank, you are consuming more of what you have already heated.  


MP- yes an interesting question.  The point being how to preheat the incoming water without consuming more fuel in doing so.  If there was an uninsulated copper loop for the cold water that could run in a circle around your basement before entering the WH maybe that would have some effect but I expect it would just draw the heat from the room forcing the furnace to work harder.   Is there some kind of coil that could run through or around the furnace / water heater’s breaching?  And if so how would it be controlled? 


Red_Barchetta said:


BG9 said:
My question is why wouldn't the water heater keep the water at a constant temperature? 
 Yes, but the water coming out of your shower head is not only coming from the water heater.  Your shower control / valve mixes water from the tank with cold water from the street.  So if the cold water from the street was colder than it was in August, you have to use more hot water to reach the temperature you want at the shower head.  So not only are you using more fuel to heat the water in the tank, you are consuming more of what you have already heated. 

 I forgot about that. But the hot water from the water heater should be at a constant temperature.

As for shower heads and faucets, there its just a matter of turning the faucet valve to hotter. Dishwashers and laundry may have an issue if "hot" or "warm" is just a fixed ratio valve setting of hot and cold water.


I just take 25% fewer showers in the winter and I break even.


Red_Barchetta said:
MP- yes an interesting question.  The point being how to preheat the incoming water without consuming more fuel in doing so.  If there was an uninsulated copper loop for the cold water that could run in a circle around your basement before entering the WH maybe that would have some effect but I expect it would just draw the heat from the room forcing the furnace to work harder.   Is there some kind of coil that could run through or around the furnace / water heater’s breaching?  And if so how would it be controlled? 

Are you thinking of something like drain-water heat recovery?

https://www.energy.gov/energysaver/water-heating/drain-water-heat-recovery


sprout said:


Red_Barchetta said:
MP- yes an interesting question.  The point being how to preheat the incoming water without consuming more fuel in doing so.  If there was an uninsulated copper loop for the cold water that could run in a circle around your basement before entering the WH maybe that would have some effect but I expect it would just draw the heat from the room forcing the furnace to work harder.   Is there some kind of coil that could run through or around the furnace / water heater’s breaching?  And if so how would it be controlled? 
Are you thinking of something like drain-water heat recovery?
https://www.energy.gov/energysaver/water-heating/drain-water-heat-recovery

I looked into one of those years ago, and it was so freaking expensive it could never pay for itself.  A 2' section was about $300.


BG9, yes, the water coming out of the water heater is the same all year 'round, so long as the setting remains unchanged. The mix ratio is changed at the point of use, most commonly at the shower valve. 

Red_Barchetta said: If there was an uninsulated copper loop for the cold water that could run in a circle around your basement before entering the WH maybe that would have some effect but I expect it would just draw the heat from the room forcing the furnace to work harder.   Is there some kind of coil that could run through or around the furnace / water heater’s breaching?  And if so how would it be controlled? 

 Heat reclamation devices of all kinds exist but the fact is that a byproduct of heat exchange is condensation. Dealing with condensation is often the process that makes the whole thing impractical. 


plungy said:
I just take 25% fewer showers in the winter and I break even.

 We have a winning solution right here, folks!!


Interesting thread!  I never thought of this before!  

Do those "hot on demand" tankless water heaters do anything to solve this problem?  Not even sure how those work, just have seen them at Home Depot and such.  Wondered if you could install one right where the street water enters, so all the house water would be slightly warm even from the cold taps?  Or do they have a minimum temperature threshold that would be undesirable for, say drinking water straight from the kitchen faucet?  And would that solution use enough less energy than having the regular tank hot water heater work harder to heat colder water to make it worthwhile?


This doesn't surprise me too much. I'm from south Texas in an area where the water pipes are pretty close to the surface. Tap water is too warm to be drinkable for about four months of the year and the need for hot water in the shower goes way down. It's very common for people to keep big jars of tap water on the kitchen counter to bring it down to room temperature so it's drinkable. 


mulemom said:
Interesting thread!  I never thought of this before!  
Do those "hot on demand" tankless water heaters do anything to solve this problem?  Not even sure how those work, just have seen them at Home Depot and such.  Wondered if you could install one right where the street water enters, so all the house water would be slightly warm even from the cold taps?  Or do they have a minimum temperature threshold that would be undesirable for, say drinking water straight from the kitchen faucet?  And would that solution use enough less energy than having the regular tank hot water heater work harder to heat colder water to make it worthwhile?

 You'd be adding another expensive heat source to preheat the water which would not be practical. It would be better to just let the water heater handle the additional BTU load. 


stupid question, MP:   Can’t we simply turn up the thermostat on our water heater and mix hotter water with the cooler water?  Sorry if you’ve already addressed this.  


jeffl said:
stupid question, MP:   Can’t we simply turn up the thermostat on our water heater and mix hotter water with the cooler water?  Sorry if you’ve already addressed this.  

 Yes, you can. But it's the same thing. You'll be using more BTUs than in the warmer months. The only difference would be the position of the shower handle when setting your comfortable temperature.


I feel like my hot water is too hot now... it’s set the same on the water heater, but it’s cooler in my house now, so the water feels too hot. I tend to keep the water slightly cooler now when I shower or it feels like it burns. 


Is this really such a big problem?  So adjust your faucet a bit ... doesn't seem like a big deal to me.  I have to do it every time I take a shower due to differing spousal preferences, even though we have the dual handle faucet (one handle for temperature and one for volume.)  


Agree ^^^

For whom is it a problem?


we are having this problem. The issue is not adjusting it- for us it’s that it won’t get hot enough. Happening on one shower/tub faucet where, even turned all the way to hot, water isn’t hot enough. I guess this means some sort of regulator inside the faucet needs to be adjusted? Weird because 1) it just started doing this out of nowhere and 2) the sink faucet in the same room gets plenty hot


Without doing physics, this could be a 0 sum game,  but... say there was a heat exchanger somewhere after the water inlet into house and before hot water heater.  It would have to be large enough to meet or exceed the typical hot water flow rate.  Even heating water up based on ambient temperature of the basement ought to temper the cold water.  That said, of course I’m heating up the house, including the basement, by using fuel to run the boiler...   

Maybe a heat exchanger that warms the cold water by using heat that goes up the boiler and hot water flue pipe?

But you know given the impending demise of petroleum to heat our homes in my lifetime, we ought to put our efforts into solar/wind etc 


conandrob240 said:
we are having this problem. The issue is not adjusting it- for us it’s that it won’t get hot enough. Happening on one shower/tub faucet where, even turned all the way to hot, water isn’t hot enough. I guess this means some sort of regulator inside the faucet needs to be adjusted? Weird because 1) it just started doing this out of nowhere and 2) the sink faucet in the same room gets plenty hot

 Have you checked the temperature setting on your hot water heater?  It is often set rather low by default (or by a plumber trying to be helpful) out of concern for people (especially children) getting scalded.  We turned ours up at some point when the kids were older and it did make a difference in how many showers we could take in quick succession.


yes, it’s not the hot water heater. That’s set high and very hot water comes out everywhere else. It’s only the one shower/tub combo faucet. I can only conclude the gauge inside that faucet somehow re-set itself or is broken 


the previous owners installed Moen temptrol mixing valves.  I’ve had to replace them once, because they simply no longer mixed hot/cold correctly anymore.  In my shower, it would not get beyond just barely warm.  They have a lifetime warranty fortunately, otherwise several hundred dollars each to replace.  I’m pretty sure another one has stopped working (after a year).  Depending on what type of mixing valve your bath has - it may need replacement



dickf3 said:
Agree ^^^
For whom is it a problem?

 I posted this after fielding a call from a customer saying their shower water was not as hot as it used to be. The sinks and basins were all the same typical temperature. Just not the shower when the temperature handle was in its usual position. The issue was as I described. The now-cooler cold water is affecting the shower temperature. They compensate now and it's fine. 


what does “they compensate now” mean exactly?


Peteglider, tell me more about “mixing valves”?


conandrob240 said:
what does “they compensate now” mean exactly?


Peteglider, tell me more about “mixing valves”?

 It’s a thermostatic valve, that’s designed to do 2 things - keep the temperature constant, so even if someone say starts dishwasher, the shower stays the same temperature, and prevent scalding high temperatures.  In my previous house I installed Grohe vaLoves, which performed flawlessly and were never a problem.  The Moen ones work great, but as best I can tell they either get dirt in them (and they’re not servicable/cleanable) or something just degrades.  

Here’s an example (and you can buy any of a number of trims for it).  With this you also need volume controls for each shower head or body sprays. 


https://www.moen.com/products/Moen/Moen_ExactTempR_34_IPS_connection_includes_check_stops_thermostatic/S3371



A shower valve is an example of a mixing valve. Aside from that, most external mixing valves are temperature (thermostatically) controlled. Most shower valves sold are pressure balanced since the '90s. It's two different methods of meeting one goal: limit water temperature fluctuations. 


plungy said:
I just take 25% fewer showers in the winter and I break even.

 Now that explains a lot!



peteglider said:


conandrob240 said:
what does “they compensate now” mean exactly?


Peteglider, tell me more about “mixing valves”?
 It’s a thermostatic valve, that’s designed to do 2 things - keep the temperature constant, so even if someone say starts dishwasher, the shower stays the same temperature, and prevent scalding high temperatures.  In my previous house I installed Grohe vaLoves, which performed flawlessly and were never a problem.  The Moen ones work great, but as best I can tell they either get dirt in them (and they’re not servicable/cleanable) or something just degrades.  
Here’s an example (and you can buy any of a number of trims for it).  With this you also need volume controls for each shower head or body sprays. 


https://www.moen.com/products/Moen/Moen_ExactTempR_34_IPS_connection_includes_check_stops_thermostatic/S3371

 If this is a Moen Shower, Moen has a lifetime free replacement program for cartridges and the Spooler which is the hot-cold mixer valve.

Just call them, register on the phone and get the new parts.  Then pay a good plumber to put them in.

Oh, how do I know this?  Spooler hung up.  One of the Good plumbers here told me to call and get the parts for free or pay about $150-$200 to buy them.



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