Low Flow and won't heat

[BayouBiker]

The modern Atwood/Dometic water heaters being describe here have thermostatically controlled anti-scald mixing valves as you speculated. They are not adjustable because as you surmised, they are themo mechanical. as other indicated the only practical service is to soak them in an acid solution to clear out scale and corrosion and loosen debris.

I am not familiar with the 2002 Classics but when I look at your parts and owners manuals I don't see anything indicating your setup included a mixing valve. The plumbing schematics indicate you do not.

[bibbs]

Originally Posted by bartzstream2

I think I might be the dope here, but I have never heard of a mixing valve in my RV. The pics make it appear to be near or part of the water heater. I hope someone can enlighten me. Is it a thermostatically (mechanical thermostat) controlled anti-scald device? I hope someone can help me understand this valve and get removed from dope status.

Yes it’s a thermal- mechanical mixing device, anti scald, would be the purpose. I have never seen them in the older trailers, we would just mix our water, it where we were using it, at the faucet. They have springs and valves that get scale/ crud in them, so they mess up.

[Al and Missy]

Originally Posted by bartzstream2

I think I might be the dope here, but I have never heard of a mixing valve in my RV. The pics make it appear to be near or part of the water heater. I hope someone can enlighten me. Is it a thermostatically (mechanical thermostat) controlled anti-scald device? I hope someone can help me understand this valve and get removed from dope status.

I don't think trailers of that vintage had a mixing valve. Mine doesn't. It's a safety/anti-litigious feature to keep people from scalding themselves. Didn't become common until years after our trailer were manufactured.

Al

[bartzstream2]

Originally Posted by bartzstream2

I think I might be the dope here, but I have never heard of a mixing valve in my RV. The pics make it appear to be near or part of the water heater. I hope someone can enlighten me. Is it a thermostatically (mechanical thermostat) controlled anti-scald device? I hope someone can help me understand this valve and get removed from dope status.

Thanks to the several people who replied to enlighten me onthe mixing valve. As one pointed out, mine is too old to have a factory-installed one. I will note that sometimes when I need the hot water to keep up, so to speak, I use both the electric element and the propane to get a fast recovery, and have measured the water temp at over 135 degrees, which is of course, scalding.

[aftermath]

I installed a water heater in my tent trailer way back in the 80s. It came with an easy to set thermostat. I had young children at the time so we kept it in the "safe" range. My 2006 Airstream does not have a thermostat which makes it a challenge. Apparently the newer heaters are putting out water that is too hot so what did the engineers do, they developed a mixing valve. This valve has complicated an otherwise easy fix. Now we have valves that clog up and are not so easy to get to. If they made a thermostat for the tank, like they used to have, it might have been better. You think?

[bickp]

Since the trailer is still under warranty, I sent a note to JC asking them for parts (HWH mixing valve and sail switch for furnace that's not working) since I can't get into closed dealerships. In a reply email they asked for the vin, so I am hoping to get some parts one of these days. If so, the mixing valve will be a spare.

Installed the purchased mixing valve today. It came with white pipe tape installed on the male end that fits into the heater. I replaced that with PTFE sealant.

Before reinstalling I attempted to clean the female threads in the tank with an old toothbrush. There has got to be a better way to clean threads because the toothbrush method was pretty lame. Hoping the sealant compensates for my lousy job. Suggestions (for next time hopefully) about the best way to clean out the female threads are welcome. I'll wait 24 hours before testing. Probably longer since we've got hard freezes coming this weekend.

Question about the old mixing valve: I am going to soak it in in CLR as some have suggested. Wondering if I should drop the entire valve, including the black plastic end into the CLR? Or somehow keep the plastic part out of the liquid.

thanks all,

bickp

[BayouBiker]

drop it all in, the plastics are not reactive to the acids or cleaning agents in CLR or any other hard water cleaner.

cleaning female threads? Only good way is to chase the threads with a tap, but that's not realistic for any of us. Plumbers I've observed simply add new pipe dope or Teflon tape and tighten it til it don't leak.

[bartzstream2]

Originally Posted by BayouBiker

drop it all in, the plastics are not reactive to the acids or cleaning agents in CLR or any other hard water cleaner.

cleaning female threads? Only good way is to chase the threads with a tap, but that's not realistic for any of us. Plumbers I've observed simply add new pipe dope or Teflon tape and tighten it til it don't leak.

Buy a nipple or other fitting of the correct size to thread into the old valve and use a hacksaw to cut across the threads to create a cutting edge to remove the old sealant or tape. I use this method (with a bolt or a nut, depending on whether I need a tap or a die in a size I don't have) and use it to chase or clean up the threads.

[BayouBiker]

Nice plan! I've seen that done too a long while ago. Initial thought was it's a lot of funny business but on reflection it really is a good cheap easy solution.

[bickp]

Originally Posted by bartzstream2

Buy a nipple or other fitting of the correct size to thread into the old valve and use a hacksaw to cut across the threads to create a cutting edge to remove the old sealant or tape. I use this method (with a bolt or a nut, depending on whether I need a tap or a die in a size I don't have) and use it to chase or clean up the threads.

Great idea. I'm hoping that yesterday's job holds, but from all of my reading it sounds like I'll be removing the mixing valve every now and then for clean up. I'll try your suggestion next time around.

[Too tall]

Originally Posted by bickp

Great idea. I'm hoping that yesterday's job holds, but from all of my reading it sounds like I'll be removing the mixing valve every now and then for clean up. I'll try your suggestion next time around.

Since we are are/were in similar boats can I offer my plan to avoid R&R this valve every year?


First, if we use the trailer all season long I plan to shut off the winterizing valve, drain the HW tank and flush it with a wand. This should eject the calcified minerals that cause this problem. Second and probably overkill we now have a two stage (external) water filter so that no particulates will get into the trailers water tanks dot period. During a long camping season I'd anticipate flushing the tank twice.



This seems reasonable?

[BayouBiker]

Calcium and Magnesium Carbonates are less soluble at higher temperatures and lower pressures so they tend to solidify in the water tank and in valves and faucets.

Another excellent way to reduce hard water issues is to turn off heat to the tank when you're ready to pack up. Then while draining the grey water, run a bunch of water through the hot water system both faucets wide open. You'll have to do it each time to prevent it from building up and hardening in the valve, so it will flush out each time.

[bickp]

Finally it is not dropping to freezing in Michigan at night. The new mixing valve is in. I hooked up the hose to the city water port. Turned on the hot water in the bathroom to clear out the air as I filled the hot water tank.
Same result. Very low flow on the hot water side, great flow on the cold water side. Same thing in the kitchen shower and outside shower. Same result with city water or on the pump with fresh water tank.







So you don't need to re-read the entire thread: I've
- emptied and refilled the hot water heater a half dozen times
-gently tapped the mixing valve with a hammer to dislodge whatever
- Bought the gadget that squirts out junk in the bottom of the tank. No junk came out
- removed all the sink spout screens, closed the HW heater bypass and hooked up the compressor to blow out anything that might be in the lines. Didn't see anything.
-Closed all the faucets, opened the bypass and blew out the HW heater. Nothing comes out.
We consensed that it must be the mixing valve. Bought one, then thought to ask JC since it is in warranty. Now have 2 new valves.
Installed one a few weeks back.
-During process today, verified no leaks, at least nothing coming out of the bottom of the trailer or anywhere inside that I can see. No leaks at the new valve.
- Hot water flow is half or less of cold water flow.
Could not upload video so tried to demonstrate with pic's.
Needing a silver bullet if someone has one.
Bick

[BayouBiker]

You may be able to isolate the problem by running the cold water into a bucket and timing how long it takes to fill a gallon. You may need to use the shower after removing the flow limiting shower head for this test to get a good comparison. Compare that to the pump specifications for your model. Then test the rate at the hot water tank out the drain.