Atwood Mixing Valve Repair

HB Phil · 10-13-2011, 05:00 PM

Symptom: A gush of hot water followed by only luke warm water from the Atwood xt 10 gallon water heater with the mixing valve.

I drilled out the center glob of glue and solder from the gray cap of the mixing valve in order to remove the cap. There are sets of spines on the valve: The lower, large set of splines is immovable and engages the bottom edge of the cap cap and prevents it from turning. The upper, smaller set of splines turns the valve mechanism and engages the cap in the middle/top. You can re-partially re-install the cap so the bottom splines are not engaged, but the top ones are, and use the cap to open/close the valve mechanism. Incribed on the cap is the word "warmer" with an counter-clockwise arrow. I opened the valve mechanism, counter clockwise, all the way and turned on teh gas heater and heated the water until the auto shut-off.

The water was about 160 as measured at the outdoor shower when spraying it into a coffee cup with a meat thermometer in it - giving it plenty of time for the hose water to clear and for the temp of the water being sprayed in the cup to stabilize.

I then incrementally turned the valve clockwise until the wqater temp stabilized at about 125. This was about 5-6 turns clockwise.

The valve/mixer is operational. Well see how it goes after wintgerizing. I will take speciall effort to get anti freeze into the valve and clear any plain water in there before closing the water heater by-pass. But even if I have trouble, I now know how to clear it and get it operational - thanks to you guys!

Next project is replacing the cursed Shurflo 5.7 extreme POS jackhammer with an Aquatec/Aquajet 5.3 gpm water pump that Rick from rvfilters is sending over. In all fairness I made the Shurflo perform and it ran nice once it stabilized, but it fianally but the dust on our last camping trip.

We exclusively boondock. I retired 2 years ago and moved to Colorado Springs so I am no longer actually HB Phil (Huntington Beach) but CS Phil!

Thank you all for the mixing valve fix. BTW I didn
t bother with the boiling venegar treatment. Its working fine foir now. We'll see how it goes.

Tom SKP · 10-17-2011, 11:24 AM

FYI, Lots of discussion about this here:

Atwood hot-water heater mixing valve

HB Phil · 10-17-2011, 11:28 AM

I tried posing to that thread but it was closed to adding more comments. Thank you for linking them, which I should have done. That thread is where I got the info to do/fix mine rather than buying a new one. Thanks Tom. And thanks to all of those who pionnered the fix...saved me at least $150.

Endeavor2BnC · 10-18-2011, 02:49 PM

Quote:

Originally Posted by HB Phil

Symptom: A gush of hot water followed by only luke warm water from the Atwood xt 10 gallon water heater with the mixing valve.

I drilled out the center glob of glue and solder from the gray cap of the mixing valve in order to remove the cap. There are sets of spines on the valve: The lower, large set of splines is immovable and engages the bottom edge of the cap cap and prevents it from turning. The upper, smaller set of splines turns the valve mechanism and engages the cap in the middle/top. You can re-partially re-install the cap so the bottom splines are not engaged, but the top ones are, and use the cap to open/close the valve mechanism. Incribed on the cap is the word "warmer" with an counter-clockwise arrow. I opened the valve mechanism, counter clockwise, all the way and turned on teh gas heater and heated the water until the auto shut-off.

The water was about 160 as measured at the outdoor shower when spraying it into a coffee cup with a meat thermometer in it - giving it plenty of time for the hose water to clear and for the temp of the water being sprayed in the cup to stabilize.

I then incrementally turned the valve clockwise until the wqater temp stabilized at about 125. This was about 5-6 turns clockwise.

The valve/mixer is operational. Well see how it goes after wintgerizing. I will take speciall effort to get anti freeze into the valve and clear any plain water in there before closing the water heater by-pass. But even if I have trouble, I now know how to clear it and get it operational - thanks to you guys!

Next project is replacing the cursed Shurflo 5.7 extreme POS jackhammer with an Aquatec/Aquajet 5.3 gpm water pump that Rick from rvfilters is sending over. In all fairness I made the Shurflo perform and it ran nice once it stabilized, but it fianally but the dust on our last camping trip.

We exclusively boondock. I retired 2 years ago and moved to Colorado Springs so I am no longer actually HB Phil (Huntington Beach) but CS Phil!

Thank you all for the mixing valve fix. BTW I didn
t bother with the boiling venegar treatment. Its working fine foir now. We'll see how it goes.

I'm a little confused. Why do you want to turn the temp down? I would have thought that the hot water would last longer if you started out with hotter water. You'd use less hot water and more cold water to get to a comfortable temp. If the hot water is cooler to start with, you'd use more hot water with less cool water thereby decreasing the overall usable capacity of the hot water. I'm confused!

HB Phil · 10-18-2011, 03:05 PM

160 is dangerously/scalding hot. 125-130 is plenty hot, steaming. The heater makes excessively hot water to "mix" with incoming unheated water in the mixing valve. The tank hold 10 gallons but you get 16 gallons of normalthe 120 degree water mixing the over heated water. That is the whle point of the over heated water and the mixing valve. Folks, including me, were having problems with the mixing vlave sticking so that it only delivered luke warm water, despite the fact that the water in the tank was 160-180.

rons6144 · 11-26-2011, 04:24 PM

Thanks for this post about the sticking mixing valve. I'm going to try to get the gray knob off tomorrow and do what you said and hopefully it will get rid of the blockage. Been having luke warm water inside the rv sporadically for a couple weeks, even though the tank water is very hot.

rockintom · 11-26-2011, 04:34 PM

Quote:

Originally Posted by rons6144

Thanks for this post about the sticking mixing valve. I'm going to try to get the gray knob off tomorrow and do what you said and hopefully it will get rid of the blockage. Been having luke warm water inside the rv sporadically for a couple weeks, even though the tank water is very hot.

Guarantee that is your problem. As long as you have checked to make sure your outside shower/faucet has not been left on. That will give you luke warm water inside too. rockin'

Erlingiii · 05-13-2012, 12:18 PM

I have been dealing with Luke warm water for some time now, picked up a #1 grab it screw extractor from lowes for 8 bucks, and the whole job took about fifteen minutes. My wh is located under a stack of drawers, so I had to take out three drawers and one crossmember (4 pocket screws) to get my body into the void where the heater is positioned. The screw holding the tamper preventing cap was facing away from me, but still managed to flawlessly remove the screw without causing any damage which allowed me to replace the safety cap and swap the old screw with a thumb screw. The cap locks the valve which prevents any changes that could occur from vibration and what not, while the thumb screw secures the cap and allows for easy future adjustment. I appreciate the advice I've read, and hope others find my experience helpful. I now have HOT showers and cleaner dishes!

Jim & Bona · 05-15-2012, 04:51 AM

Quote:

Originally Posted by Endeavor2BnC

I'm a little confused. Why do you want to turn the temp down? I would have thought that the hot water would last longer if you started out with hotter water. You'd use less hot water and more cold water to get to a comfortable temp. If the hot water is cooler to start with, you'd use more hot water with less cool water thereby decreasing the overall usable capacity of the hot water. I'm confused!

Tim, it seems to me that the temperature of the hot water post mixing valve has a sum zero effect on the overall useable hot water due to the fact that the water in the heater tank is a fixed amount at a fixed temperature. Changing the temperature which the mixing valve produces only changes the point at which you add more or less cold water, that being the faucet at the sink. In other words, there is a fixed amount of energy available in the tank and where you choose to temper it to a useable temperature doesn't affect that amount of energy.

Right, Tom?

Jim

Endeavor2BnC · 05-15-2012, 08:49 AM

Quote:

Originally Posted by Jim & Bona

Tim, it seems to me that the temperature of the hot water post mixing valve has a sum zero effect on the overall useable hot water due to the fact that the water in the heater tank is a fixed amount at a fixed temperature. Changing the temperature which the mixing valve produces only changes the point at which you add more or less cold water, that being the faucet at the sink. In other words, there is a fixed amount of energy available in the tank and where you choose to temper it to a useable temperature doesn't affect that amount of energy.

Right, Tom?

Jim

Jim,

You're right. There is a fixed amount of energy in the tank. Raise the temp = more stored energy available. More stored energy = longer hot water showers. One just has to be careful, when using hotter water, to add more cold water to get it to a comfortable water temp. DW likes the longer showers too. Keeping DW happy is important for more fishing days.

rockintom · 05-15-2012, 10:09 AM

Quote:

Originally Posted by Jim & Bona

Tim, it seems to me that the temperature of the hot water post mixing valve has a sum zero effect on the overall useable hot water due to the fact that the water in the heater tank is a fixed amount at a fixed temperature. Changing the temperature which the mixing valve produces only changes the point at which you add more or less cold water, that being the faucet at the sink. In other words, there is a fixed amount of energy available in the tank and where you choose to temper it to a useable temperature doesn't affect that amount of energy.

Right, Tom?

Jim

Sorry Jim, I gotta agree with 99 on this one. BUT only on our Atwood mixing valve system. Since the purpose of the mixing valve is to adjust the blends of superheated water and tap water to give you the Atwoods ideal hot water at the faucet. Just FYI......those numbers are 1) superheated tank hot water ~180*F 2) And faucet water ~120*F. All things kept equal...if you raise the tank water temp then that would yield more water at the faucet water. However, if you raise the mix valve temp then technicially (all other things equal) then you would yield less water at the faucet. Clear as mud huh.....now I'm sounding like you!!!
rockybaby.

Need to get back to something my interesting, like polishing rocks!!

rons6144 · 05-15-2012, 10:54 AM

Just wanted to advise I did the temp. knob deal and it didn't help. Took the valve off and cleaned it, but still didn't help. Finally, just broke down and bought a new one direct from Atwood. Cost only $120.00, think the lady felt sorry for me and she knew that the valve has been a major malfunction for lots and lots of people.
She pointed out that the new valve has a filter screen on the inlet where the hot water enters the valve from the water heater. This supposedly keeps the minerals from entering the valve and ruining it. If it gets clogged, you can just remove it and clean the screen.
Any way, it is so good to haved really good hot water again. Never would have figured out what the problem was without you guys help. Several RV repair places where I asked for help had never heard of a mixing valve. I am happy, and more important, my wife is, also
Ronnie

gdbontly · 05-15-2012, 01:42 PM

I should knock on wood (okay, I just did), but I've never had any problems with my water heater. I heard that winterizing the system has caused some issues, but I've never winterized our house. And now hearing that mineral build up may cause problems as well, I happy to have our On The Go water softener. After almost 2 years of full time living, there's no crusty stuff on any of the faucets or the shower head. Seems the softener was money well spent.

rockintom · 05-15-2012, 02:06 PM

Quote:

Originally Posted by gdbontly

I should knock on wood (okay, I just did), but I've never had any problems with my water heater. I heard that winterizing the system has caused some issues, but I've never winterized our house. And now hearing that mineral build up may cause problems as well, I happy to have our On The Go water softener. After almost 2 years of full time living, there's no crusty stuff on any of the faucets or the shower head. Seems the softener was money well spent.

Glenn, I'm so glad you listen to me and do what I do!!! You are such a smart man!!!!