Weird Hot Water Issues

[recentcoin]

The sinks are little touchy but ok once you figure it out how to adjust the temprature. The problem is the shower. If you stop the water using the valve at the shower head, the water comes out smoking hot when you turn it back on. Adjusting the temperature in the shower is super tricky too. Its either COLD or HOT. Its really hard to get anything thats anywhere in the middle. Since I like actually having skin, I tend to end up wasting quite a bit of the hot water while trying to get it adjusted.

Its a Thor Hurricane from 2011 that is on loan to us from our in laws. I don't mind fixing things as a thank you for letting us use it, so what I would like ot know is what the likely problems are and how easy it might be to attempt to fix or at least make the skin peeling showers less of an issue. We are pretty good at DIY on all sorts of things.

[groswald]

Originally Posted by recentcoin

If you stop the water using the valve at the shower head, the water comes out smoking hot when you turn it back on.

I've wondered at this phenomenon for years. It's definitely not unique to your motorhome (happens in my current & previous MHs, and home shower). Try it with almost any hand-held shower with an on/off button and you'll have the joy of experiencing it!

I've never found a satisfactory answer for why it happens. I've always wondered if it's actually an illusion. Your wet bod cools very quickly. When you re-start the flow of hot water it feels (much) much hotter than it is.

You can see this at work by getting two large bowls of water. Fill one bowl with ice and cold water, the other with hot water (not too hot though). Put your hand in the hot water for 1 minute. Then put it in the cold water for 1 minute. Then plunge your hand back in the hot water. It hasn't gotten any warmer, but it'll sure feel like it has!

This is my theory. Not great, but it's all I've got.

It'd be great if someone who actually knows will share!

[shootist]

Does the thor have a mixing valve after the water heater?

[Outbound]

I also get minor temperature swings, not as bad as mentioned, I find if I valve on/off while showering with hand held I do not get temp swing.

[Old-Biscuit]

When you stop shower water via the button/lever on handle the shower faucet becomes a mixing chamber.
Hot water is at higher pressure so it will flow out First when you open the button/lever until hot/cold balance and mix
*Cold water supply (city or pump can be 50-55#. Hot water from water heater can be 120-125# --- water swells when heated/swelling increases pressure)

Installing an adjustable mixing valve on the hot/cold lines at shower can help...course you need workable access

Turning the shower Head AWAY from you before turning it back on is FREE

What is source of the Hot water....Brand/Model of heater??

[alank]

From what you describe, I suspect the water heater is producing excessively hot water. You might want to measure the temp. of the water. Could be a water heater thermostat issue.

[groswald]

Old Biscuit,

THANK YOU! Makes perfect sense. I can now die happy having seen that mystery solved.

Alank,

Both Atwood and Suburban (tanked) water heaters come pre-set to 140 degrees. It's done so you can get a complete shower with just 6 gallons of hot water (to mix with cold to get a useable temp). It's too hot to be safe, but it's been that way for a very long time. It's the main reason I prefer knobs to levers on the shower valves - less likely to knock one with an elbow and shut off the cold water.

The standard thermostats are fixed and can't be adjusted. You can buy a replacement 120 degree unit from Atwood. Not sure about Suburban.

I don't know of many RVs that have mixing valves, just separate knobs for hot and cold. Some of the high end DPs and customs may have 'em. Not sure about my Tiffin, but I think I'll find out.

Regards,

Randy

[Dav L]

Originally Posted by Old-Biscuit

When you stop shower water via the button/lever on handle the shower faucet becomes a mixing chamber.
Hot water is at higher pressure so it will flow out First when you open the button/lever until hot/cold balance and mix
*Cold water supply (city or pump can be 50-55#. Hot water from water heater can be 120-125# --- water swells when heated/swelling increases pressure)

Installing an adjustable mixing valve on the hot/cold lines at shower can help...course you need workable access

Turning the shower Head AWAY from you before turning it back on is FREE

What is source of the Hot water....Brand/Model of heater??

Excellent post. Should be listed in the "Plumbing" future forum category I have just UpVoted this post At least in my own head...

[Old-Biscuit]

Originally Posted by groswald

Old Biscuit,

THANK YOU! Makes perfect sense. I can now die happy having seen that mystery solved.

Alank,

Both Atwood and Suburban (tanked) water heaters come pre-set to 140 degrees. It's done so you can get a complete shower with just 6 gallons of hot water (to mix with cold to get a useable temp). It's too hot to be safe, but it's been that way for a very long time. It's the main reason I prefer knobs to levers on the shower valves - less likely to knock one with an elbow and shut off the cold water.

The standard thermostats are fixed and can't be adjusted. You can buy a replacement 120 degree unit from Atwood. Not sure about Suburban.

I don't know of many RVs that have mixing valves, just separate knobs for hot and cold. Some of the high end DPs and customs may have 'em. Not sure about my Tiffin, but I think I'll find out.

Regards,

Randy

Atwood T-stat is 140*F & ECO is 180*F
*T-stat Closes for reheat cycle at 110*F
**ECO will reclose at 150*F...but Fault Light/Lockout has to be reset by turning switch OFF/back ON

Optional T-stats are 130*F...but many websites list them as 120*F (Atwood does have a 120*F optional t-stat anymore....haven't for many years

Atwood does have an Optional an 'Adjustable' T-stat... 110*F - 150*F (replaces OEM T-stat---same position with a bracket
****I'm not fond of them...bracket is flimsy, hard to reinsulate and rheostat contacts corrode due to exposure to elements

Note since 2004 only One Set of T-stat/ECO needed for electric & propane operation----DC Controls for both functions

Atwood has an XT Model that uses a 'Mixing Valve"
T-stat is set for 160*F (ECO still at 180*F)
Mixing Valve Output is set for 130*F (Factory Sealed ---Fixed temp BUT one can remove seal and adjust output temps. Biggest issue is Hot to inlet of Mixing Valve gets clogged/scale-calcium and no more hot just like warm of COLD ----PITA

This Years Model......New Atwood 6 gal and the '9 gal XT version' have been revised to incorporate the Electric Element into the Front of WH Tank vs Backside of the previous versions
Combustion/Exhaust Chamber has be 'stacked' in the middle section of tank so element could be installed on right lower section (Outside compartment)

Previous versions used a Diagonal Combustion/Exhaust 'U' Tube that afforded greater surface area for heat transfer
Not sure how the 'Stack' Tube compares with the Diagonal for heat transfer (Atwood was a bit better vs Suburban cause Suburban uses a 'stacked' Tube on far right side. They compensated by using a 12,000btu burner assembly vs Atwoods 10,000btu one



Suburban T-stat is 130*F & High Temp T-stat is 170*F
*T-stat closes for reheat at 100*F
**High Temp has to be 'Manually' Reset via Push Button when temps have dropped below 140*F

Suburban has an Option set 140*F/180*F

Suburban uses two separate sets
120VAC Set for Electric element
12VDC set for Propane
**So when replacing make sure you get the correct voltage set



^^^^^^probably more info about RV Tank Water Heaters then you wanted/needed to know

[groswald]

Old Biscuit,

Thanks again for the great info. I wasn't aware that the 120 degree Atwood thermostat is no longer available. I've got one in my "possibly useful stuff" drawer in our coach as a spare. Purchased it in 2015, I think.

Regards,

Randy

[Old-Biscuit]

Originally Posted by groswald

Old Biscuit,

Thanks again for the great info. I wasn't aware that the 120 degree Atwood thermostat is no longer available. I've got one in my "possibly useful stuff" drawer in our coach as a spare. Purchased it in 2015, I think.

Regards,

Randy

Yes Atwood use to have 3 pre-set t-stats
The 140*F OEM, the 130*F and the 120*F
Then they added the Adjustable one to lineup
Then they Dropped the 120*F ....wasn't a big seller

And the Mixing Valve XT models with the 160*F T-stat
*** It uses a Pin Post vs a spade on one connection so it can not be used on Standard WH w/o a mixing valve (UNLESS Mods are made---then it's all bets OFF)

[recentcoin]

I am fairly certain its an Atwood but I will have to dig through the paper work to see if I can find the model number. The water that comes out is hot enough to make me dance around and say bad words before I can move it. Not a lot of room in these showers to duck and dodge the spray but I am certain that I could at least blanch veggies or poach an egg! Since my in laws have grandkids who are a bit on the younger side, I am just thankful they are not tall enough to reach the valve on the shower head.

The best water heater I ever had was actually a boiler that heated water to 240F and then down blended it with cold water to make tap ready hot water. It also regenerated faster than the taps could drain it. Talk about eternal hot water! I wonder why they don't do something similar with these. I suppose that would have to do with the water pressure being higher on the hot side than the cold side.

Engineering challenge accepted. Let me see what I can come up that works and if I figure out before we hand this back, I will let you know what I come up with. I have an idea that involves one of those air bladder pressure tanks to up the water pressure so that you can inject some cold into the hot which would serve a dual purpose. One it would make the hot last longer and two it would make the hot be hot instead of OMFG THAT'S HOT!

[windsorbill]

take a look at this.

https://www.youtube.com/watch?v=BpnNZWdlcfc&t=720s

[Cat]

Like Old Biscuit said is the easy way- turn the shower head away. Lol
But I got tired of it- the temperature changes anytime a faucet was turned on somewhere in the coach, I also was tired of those names I was called when I did it . I bought inexpensive thermostatic shower valve $45.00on Amazon. And have solved those problems. The hard part is the wall mounting. But once you do it-Its great, and I think it saves water, since the temperature know is all ready set you just turn on the flow valve and the temperature is automatically set. Safe Travels