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**Hans627** · 12-14-2018, 06:04 PM

Today I developed a problem with my hot water heater. I filled it with water (after winterizing it) and now I get a low flow and cold water from the hot water faucet. Based on what I've read on the forum and seen on YouTube it appears to be a mixing valve issue.

First of all is the picture I've attached the mixing valve? If so, can it be relatively easily replaced or does it require a RV/AS technician? It looks like something I could do if this is the mixing valve. Or is there more to it than meets the eye?

If I can replace it I plan to ask AS to supply a new one as it is under warranty.

Thoughts? Recommendations?

Thanks!

Martee · 12-14-2018, 06:24 PM

Yes indeed, that is the mixing valve.
The low flow rate is most likely related to blocked screens on the valve. You can purchase a replacement at most RV dealers with parts supply. Just give them Atwood model number. Keep the old mixing valve as a backup, after you clean the screens. Perhaps flushing the system as you winterized, freed up some debris and block your screens.

Installation is quite easy. Just make sure you use a plumbers thread sealer, use either tape or the sealer paste.

BAB · 12-14-2018, 06:35 PM

I had to replace mine in June. It was over $100. Removed the old one and cleaned it out (as much as I could). I’ll keep it as a backup. Not that hard to swap it out, especially if you have end wrenches.

**Hans627** · 12-15-2018, 05:52 PM

Quote:

Originally Posted by BAB

I had to replace mine in June. It was over $100. Removed the old one and cleaned it out (as much as I could). I’ll keep it as a backup. Not that hard to swap it out, especially if you have end wrenches.

Thanks!

Would it make sense to try to remove it and clean it?

Edistobob · 12-15-2018, 07:41 PM

The cleaning service procedure is described in the manual. As I recall it is simply cleaning the screens and soaking entire valve in hot white vinegar. I replaced mine but also serviced the old one so that I would have a spare. Didn't test it but the vinegar procedure dissolved a lot of crud. Looks like new again

**Hans627** · 12-16-2018, 06:17 AM

Quote:

Originally Posted by Edistobob

The cleaning service procedure is described in the manual. As I recall it is simply cleaning the screens and soaking entire valve in hot white vinegar. I replaced mine but also serviced the old one so that I would have a spare. Didn't test it but the vinegar procedure dissolved a lot of crud. Looks like new again

Which manual are you referring to? I looked in the owners manual and there is no mention of the mixing valve.

Thanks!

Martee · 12-16-2018, 07:38 AM

I checked my Atwood heater manual, and also nothing mentioned on the mixing valve. Which is why its discussed in this Airsteam forum, and just about every other RV forum.

Recommended cleaning procedure is to soak the mixing valve in hot vinegar to dissolve any hard water deposits blocking the screens. If the debris is not hard water related, the vinegar cleaning method is not going to work.

Disassemble of the mixing valve for cleaning of the screens is not possible, as it's a fully pressed valve unit from the factory. So most everyone, just buys a new mixing valve, and installs that unit, while working on the old one as a backup. In my case, I simply and very carefully drilled out the fine mesh screen on my backup unit. I carry that backup mixing valve everywhere I travel.

My AS was a 2018 FC25FB and the blockage appeared to be mainly plastic and metal from the factory, and so the hot vinegar soaking method was unsuccessful for me.

Edistobob · 12-16-2018, 08:39 AM

Quote:

Originally Posted by Hans627

Which manual are you referring to? I looked in the owners manual and there is no mention of the mixing valve.

Thanks!

Sorry, but my recollection of its being in the manual was faulty. I cannot find where I found the recommended service procedure; however, Martee's post (#7) is spot on. I boiled mine in hot vinegar with good cleaning results but, as I noted, I have it as a spare after buying a new one.

I do have a copy of Atwood's preventive maintenance requirements for their water heaters and here is a quote for the XT model: "...you may have to have the Mixing Valve serviced by a Certified Service Technician". I just cannot relocate the reference I came across when I did mine.

I did find a decent video discussing the generic issue at this link:

https://www.youtube.com/watch?v=ccIM5pYO0EY

but it doesn't say much more than Martee said.

Good luck!

rbs · 12-24-2018, 06:44 AM

we have suffered the mixing valve issue several times, and most of the time we have had the valve actually start working again in within 24 hours, by turning the hot water heater on and every so often run the bathroom sink faucet and you will get a short spurt of hot water. Keep doing it and with some luck the thing will free itself up and start working fine. We did purchase a new one and have changed them out a couple of times too. Getting the original mixing valve off the tank was a huge challenge, it had been installed with some type of plumber's putty and extremely tight, but after a lot of effort and loud and choice words it did come off. Now it has teflon tape and is tightened just past hand tight to line everything up, and no leaks, and a lot less effort to remove. Hot showers, nothing like'em

Mixing valve model # 90029, and you are able to adjust the temp of the water by removing the black knob, you'll see a 7mm nut (metric) and turning it clockwise will add more cold water, obviously counter clockwise will be hotter. I just drop the removed valve in a container of CLR and leave it there until I remember it and it seems to do the job, although the hot vinegar probably is a faster solution.

gnowlin · 12-24-2018, 03:20 PM

I had the same issue as mentioned with the hot water not available from all faucets and noted all the replies on the forum. I was on the road and did not want to start with the removal of the mixing valve ( just looked too hard and i'm not sure what tools I need to have to get it out?????). so, I just tapped the value several times ( about 6-8) with my cresent and cleaned out the heater with the "plastic wand" several times. got a lot of white granules out. filled up the water heater and had hot water the rest of the trip ( about 2 more weeks). actually it works just fine now.
.I will try to put a new one in but would like to find out the tool that is best to remove. also if vinegar is installed in the water heater, does someone have a recommendation how to put it in. do you pump it in? or what?

KelloggKid · 12-24-2018, 03:48 PM

Our hot water heater did the same thing last spring when we dewinterized it. Like others mentioned, the problem fixed itself over time. This year when I winterized I flushed the water tank out real good and plan on putting vinegar in it come spring, heating it up and flushing again.

**Hans627** · 01-03-2019, 02:34 PM

Today I installed my replacement mixing valve. It was not too difficult but the old mixing valve was really tight and it took some force and patience to remove it from the water tank.

The AS is in a storage lot with no water in the tank so I will have to wait to make sure there are no leaks.

Thanks to all for your comments and ideas. They are appreciated!

gnowlin · 01-05-2019, 05:09 PM

I'm interested to find out if you had to use a special tool to remove or brute force with a wrench? looks like it will be hard to get leverage .
thanks!

**Hans627** · 01-05-2019, 08:49 PM

Quote:

Originally Posted by gnowlin

I'm interested to find out if you had to use a special tool to remove or brute force with a wrench? looks like it will be hard to get leverage .
thanks!

No special tool but a lot of force. The mixing valve actually screwed out of the fitting that went into the tank. I then thought I might need to make a trip to the hardware store for a socket to remove the fitting itself but with a lot of force it came loose using an adjustable wrench.

Now hopefully I got the new one tight enough.

bickp · 04-26-2020, 11:27 AM

Quote:

Originally Posted by Hans627

No special tool but a lot of force. The mixing valve actually screwed out of the fitting that went into the tank. I then thought I might need to make a trip to the hardware store for a socket to remove the fitting itself but with a lot of force it came loose using an adjustable wrench.

Now hopefully I got the new one tight enough.

Having the same issue today. Your description seems to match what has happened to me.

I want to try to clean my valve using CLR but it came off, leaving a fitting in the tank.

I'd like to just soak the valve, but I don't want to go through the exercise if the fitting (pic) could be dirty as well.

Can someone tell me if I must the piece that goes into the tank out as well. If so, I am going to need to get some sort of leverage pipe to bust it loose.

Bick

**Hans627** · 04-27-2020, 05:54 AM

Quote:

Originally Posted by bickp

Having the same issue today. Your description seems to match what has happened to me.

I want to try to clean my valve using CLR but it came off, leaving a fitting in the tank.

I'd like to just soak the valve, but I don't want to go through the exercise if the fitting (pic) could be dirty as well.

Can someone tell me if I must the piece that goes into the tank out as well. If so, I am going to need to get some sort of leverage pipe to bust it loose.

Bick

There is no absolute need to remove the brass fitting that remains in the tank. If you can see dirt and debris inside the fitting you can remove it.

However, I would be more concerned about the scale and debris that lays in the bottom of the tank. When you turn on the water that debris will be mixed through out the tank and could once again get into the mixing valve. Make sure you rinse the tank and when it is clean (no more scale comes out of the drain) reinstall the repaired mixing valve and I think you should be good.

sheriff1 · 04-27-2020, 09:25 AM

Quote:

Originally Posted by bickp

Having the same issue today. Your description seems to match what has happened to me.

I want to try to clean my valve using CLR but it came off, leaving a fitting in the tank.

I'd like to just soak the valve, but I don't want to go through the exercise if the fitting (pic) could be dirty as well.

Can someone tell me if I must the piece that goes into the tank out as well. If so, I am going to need to get some sort of leverage pipe to bust it loose.

Bick

Yes, the brass part is actually where the problem is, there is a fine screen built into it that plugs with sediment from the tank. I’ve never seen the chrome part be the problem. It just takes a socket to remove the brass part. I think it’s about 1 1/16”

**wulfraat** · 04-27-2020, 11:09 PM

^^^ x2. Need to pull the brass fitting out of the tank and clean or replace.

bickp · 04-28-2020, 08:48 AM

That's folks.
WR: great pic. No question now, that brass piece needs to come out.
sheriff1: I'm going to take a flyer on the 1 1/16 through Amazon, instead of waiting outside HD or Lowes for an hour.
Great stuff, very helpful.

sheriff1 · 04-28-2020, 08:55 AM

Quote:

Originally Posted by bickp

That's folks.

WR: great pic. No question now, that brass piece needs to come out.

sheriff1: I'm going to take a flyer on the 1 1/16 through Amazon, instead of waiting outside HD or Lowes for an hour.

Great stuff, very helpful.

Hang on, I’ll double check the size you need before you order