Need Help - Mixing Valve Leaking

BrianZ

We're supposed to leave tomorrow for our first 2018 trip in our 8 month old 2018 T@B S, but after doing the spring sanitizing flush of the water lines, I discovered water leaking from the base of the brass body of the mixing valve (see photo with arrows showing source of the leak).  There was no leakage from any of the plastic water line connectors, just between the brass & the silver colored mounting bracket.
Is there anything I can do to fix this?

As a temporary measure, I closed both hot & cold Alde bypass valves, then drained the Alde water by opening the yellow Alde drain valve plus the hot outside shower line to allow air in.  If I can't fix it, will we be ok to use the heater like this & still use the cold water for sink & toilet?

I don't understand what might have caused this, as I was very meticulous about following winterizing procedures & blowing out lines at 40 psi.

Thanks for any help or advice.
-Brian

Sharon_is_SAM

Bypassing the Alde should bypass the mixing valve and you should be able to use cold water.  There was a batch of mixing valves that were defective, so it may not be leaking due to a crack from freezing.  Either way, it is replaceable.  

BrianZ

Thank you, Sam.  I was hoping maybe something just needed tightening.  I wonder if this is covered under warranty.

Verna

@BrianZ, I was told by one of the factory guys that if you unscrewed the screw too far in adjusting the mixture, it would leak.

While I’m not sure if this applies, and please realize my 2014 did not come equipped with a mixing valve, but I thought I would just interject this piece of information.

In other words, make sure the screw is tight and the mixture of hot and cold water is what you want.

BrianZ

Thanks, Verna, but I haven't touched the plastic adjustment knob on top, or done anything with it.  Last fall, we had nice warm water, so never had any reason to make an adjustment.  I would think if the adjustment was too loose, it would leak from the top, not where the arrows show the water coming from.  Wondering if one of the hex shaped collars under the mounting bracket could need tightening.

ScottG

@BrianZ, yes, you can run the Alde for cabin heat even if there is no water in the HW tank.

I think you might be onto something with the loose hex collar idea. It certainly can't hurt much at this point to try carefully snugging things up a little and crossing your fingers. Worst case you'll still be replacing something.

Like Verna, I have an older T@B without the mixing valve. I can't say I'm disappointed about that--while the water does come out of the Alde pretty darn hot, there is already a handy "mixing valve" located at each fixture.  ;-)

If it were me I'd probably remove and bypass the valve altogether. However, the pretty darn hot I mentioned earlier can exceed 150F, so if you burn yourself you didn't get the idea from me!  :-)

BrianZ

Thanks, Scott.  We're only going for one night this time, so I may wait until after we get back & can talk to NuCamp.
The only question I'm wondering about is, should I leave the bypass valve between the hot & cold Alde lines in it's normal closed position while hot & cold valves are closed, or do I need to open the bypass valve?  If it doesn't matter I'll leave it closed, so I don't forget to close it later after the valve repair.

ericnliz

@BrianZ, I had a bad mixing valve on my 2016 T@B & it was replaced at no charge. Looking at your photo though, I see what appears to be a bleeder screw on the right side of the valve above the bracket. Are you sure it is leaking at the base, and not from that screw? Just a curiosity question....you're the one that's up close & personal with the valve.  

BrianZ

Thanks, I did check all around the valve body & never felt any dampness around the sides or top, only at the very bottom.  But I did not specifically check that screw for tightness, but I will, now that you've told me what it is.  Wonder what it's used for?

rcuomo

Brian, ditto what Eric suggested.  It’s not uncommon for the bleeder screw to have seepage.

ScottG

BrianZ said:

Thanks, Scott.  We're only going for one night this time, so I may wait until after we get back & can talk to NuCamp.
The only question I'm wondering about is, should I leave the bypass valve between the hot & cold Alde lines in it's normal closed position while hot & cold valves are closed, or do I need to open the bypass valve?  If it doesn't matter I'll leave it closed, so I don't forget to close it later after the valve repair.

I don't see any reason why the position of the bypass would matter. If you leave it closed, you just get won't get any water from the hot water taps. If you open it, you will get cold water from the hot water taps.

The cold water taps will be not be affected in any way.

Ratkity

@BrianZ - Great eagle eyes seeing the bleed screw! Kudos

Sharon_is_SAM

Scott you are right.  The Alde bypass open or closed, water still goes through the mixer valve and it will still leak.

ScottG

The way the T@B in this photo is plumbed, closing the Alde isolation valves will stop water from flowing to both the Alde and the mixing valve. I believe this is what BrianZ has done to temporarily stop the leak.

In this situation, the position of the single bypass valve doesn't matter and the cold water taps will still be operational.

BrianZ

I believe you're right, Scott.  Many thanks to ericnliz (& rcuomo), who I believe have correctly diagnosed the problem!  I was able to tighten that screw a tiny bit, less than 1/8 turn, but it did turn a bit.  I also tried to tweak the brass hex ring & black plastic one under that, both under the mounting plate, but they didn't seem to move.  I tested with more water in the tank & now with water hookup at the campsite & it has remained bone dry!  Bleeding screw seems to have been the culprit, even though I couldn't really see water coming from it.
Thanks again to all.

ericnliz

@BrianZ, Glad to help out, & very happy the problem is now resolved! I'll have to put that one in the notebook & take a look next time I have the cover off.

Subism

De-winterized and sanitized my 2016 S Max today and the pump could never build pressure, so I started looking for a leak. I found the mixing valve leaking in the same location and was able to actually see it was coming from the same screw. I was wondering what this screw was; is anyone positive it is indeed just a bleed screw? I was able to tighten it slightly and the leaking stopped, but I was hoping it was not a regulator. Seems to me this is a self-bleeding system and not sure why there would be a bleed screw anywhere (though I don't see any need for a regulator at that location either).

BrianZ

@Subism, glad I'm not the only one, but sorry for you, & thanks for letting us know.  The screw appears to have a washer under it, but it's greenish in color & looks like it's made of paper.  I'm wondering what's the best material for a washer in a location like this that is subject to extreme changes in temperature from boiling hot to below freezing.  In any case, these extremes would subject it to repeated expansion & contraction that could loosen the screw & cause leaking.  It should probably be on a checklist of routine spring maintenance, because after the cold temps of winter storage cause contraction of the metals, it would be most prone to leaking.

By the way, I only discovered the leak because I found my nylon tool bag was damp on the bottom.  It was stored in the compartment under the seat near the wheel well on the opposite passenger side.  The Alde on the driver's side was slightly uphill where we had it parked, so the water ran across the back floor to the other side, then it ran forward, because the tongue was lower for drainage during flushing the water tank.  I observed the bottom inch of wood framing was damp near the floor & followed the damp wood back towards the other side near the Alde, then saw water on top of the mixing valve mounting bracket.  I think I first noticed a coil of nylon rope in the bottom of my tool bag was completely damp, which seemed odd.

Subism

Found the mixing valve in the 2017 Tab manual and looked it up here - http://www.lkarmatur.com/en/lk-550-aquamix-_55554451.aspx#55554688. The screw is actually to aid in "draining of smaller water heaters", though it does not appear necessary with the plumbing as laid out in the Tab.

@BrianZ - thankfully, my valve did not appear to have leaked until now and did not leak too much; however, if the pump would not have continued running far too long with the faucets off during sanitizing I likely would have not found this until it was a much larger issue, as I mostly am on city water. I was surprised after fixing mine and then searching the forum that you had the same issue only a few days ago. Definitely will go on my list of things to check each spring!

rcuomo

Marc, you are correct in that the Alde systems installed in North America are self bleeding systems. But I believe the mixing valve is used globally and the screw can also be used to drain the system. The “washer” is made of common gasket material and the screw will loosen from normal system temperature expansion and contraction.  Definitely a good idea to check it as part of normal annual maintenance. 

BrianZ

Thanks for that link, @Subism .  If the scew-vent is for letting air in to drain a water heater tank, then you can see in @ScottG 's photo how I accomplished the same thing by closing the hot & cold Alde isolation water valves, opening the Alde drain, then opening the hot outside shower faucet to let air in for draining.  The outside hot shower line connects to the inside of the isolated Alde loop of plumbing.  Too bad we have a drain we don't need, which makes me wonder if that screw can be [semi]permanently sealed with loctite or something.

BrianZ

Wondering if something like this applied to the threads might help seal the screw..
https://www.amazon.com/Loctite-1716864-Plumber-Marine-Adhesive/dp/B0044F9KNU

ScottG

I vaguely recall using a plumbers "thread sealant" at one time in the distant past. It was a thinnish liquid that came in a small tube and was applied to threaded fittings. precisely to keep them from leaking. I don't recall a name or brand, but any decent plumbing store should be able to point you in the right direction.

The marine adhesive you found would probably work also.

ericnliz

@BrianZ, Just wanted to give you a big "THANKS" for bringing this issue up. I de-winterized my trailer a couple of days ago & found the bleeder screw "seeping" on the mixing valve as well. About 1/8 of a turn & it dried right up. Never had the issue before, as I inspect the water lines pretty thoroughly at the beginning & end of each season. Again, thank you for sharing, you helped at least one fellow T@BBER!!!!!  

BrianZ

Bleeder screw strikes again..
Third time is not a charm for that pesky bleeder screw in the mixing valve.  Fortunately, I just happened to discover it not too long after hooking up to city water while on the road at an RV park, so not a lot of leakage, but it was not stopped by simply tightening.  I shut off water supply, released pressure at a faucet, then removed the screw & its washer..

So, I think this shows the reason for the leak.  I'm guessing maybe the repeatedd tightening, then repeated heating & cooling may have been too much stress for the washer.
I installed a new ordinary stainless washer, which seemed to fix it.  Will have to add the Loctite to the threads later.  Maybe I said that before & never got around to it.
7-20-2021 Update:
Done.  I removed the screw, cleaned & dried it, then added the Loctite Blue 242 (heat & vibration resistant) to the threads, replaced & tightened the screw.  Hopefully, that will be the last leak from that screw.