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Thread: Moen 1222 valve not working with hot water on demand heater

  1. #1
    DIY Junior Member sandygirl's Avatar
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    Default Moen 1222 valve not working with hot water on demand heater

    My second phone call to Moen customer service, I found out from Moen that the 1222 valve has an anti-scald setting when it diverts water to the shower. The temperature of the water needs to be between 109 and 120 degrees for the valve to work properly. The Moen customer service rep said that the valve does not work with all hot water on demand heaters. They sent out a replacement valve, in case the valve was faulty.

    I replaced the valve, but the problem did not go away.

    Unfortunately, the settings on our point-of-use hot water heater does not allow us to set the temperature. The gauges on the water heater are "gas regulator" and "temperature" and they adjust from low to high within a range. So it looks like the valve does not work with our unit. It worked for a while in May when temperatures were colder outside. But I have not been able to make it work at all this summer and fall. Water temperatures are higher going into the unit.

    What happens is: I will run water into the tub turning the handle to hot. The temperature on the water heater will climb and settle at just under 120. In order for the hot water heater to work, I had to move the temperature setting to mid range. The hot water heater won't turn on when the temperature is set to the lowest setting.
    Once the water is hot and I even add some cold to where the temperature would be comfortable to shower, then I pull the shower knob to move the flow of water up to the shower. Then the temperature begins to climb. It will climb to well above 120 degrees. Now the water coming out of the shower head is too hot. When I try mixing in cold, the water heater turns off. If I don't add cold, eventually, the hot water temperature climbs so high that the hot water heater turns off. In both cases, the water temperature drops back down and the shower is now cold.

    Moen sent a new valve and I replaced it and tried again. I adjusted the temperature/gas regulator on the water heater and got the shower to work once. A few days later I tried again and it did not work again. I tried adjusting the water heater settings to no availe. I tried again the next day, same thing. It did not work.

    I called Moen again and asked if there was another valve without the anti-scald regulator built into it and Moen said NO. Only the two handle units. That valve will not work with the single handled shower/tub units. Moen's solution was to turn the water heater to it's lowest temperature setting. As we know, that doesn't work with the unit I have. The heater won't even turn on.

    I have installed this unit in a fiberglass surround tub/shower. So unfortunately, the only solution I see is to tear the shower unit out and install a different single handle, tub/shower unit, from a different manufacturer.

    Unless?...is there a generic valve or another manufacturer valve that I can try as a replacement that would work?? Has anyone run into this problem. Are there any solutions other than replacing the unit.

    I told Moen that they need to put a clear warning on their packaging with this unit that it is not compatible with all hot water on demand heaters. If I had seen a warning like this, I would have likely not bought the unit. I have a Moen unit in another bathroom that was installed in the house when it was built. So I figured I was safe and it was good quality. Not to knock quality, but very misleading and now I have to fix it or go without a shower!!! UGH!

    Any suggestions or comments. Sorry to rant.

    Thank you )

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    I do not think your issue is restricted to Moen...it is a function of the anti-scald federal requirements and the interaction of the on demand system and the flow (essentially all single handle shower valves have some sort of pressure balance valve in them to accomplish this feature). Many on demand/tankless systems adjust the flow rate based on the incoming water temperature so there's enough 'dwell time' to allow the water to reach the desired setting. THen, they have a minimum flow rate that's required to make them turn on. As a result, it is not uncommon for the hot water to be restricted in flow somewhat verses the cold water supply. This creates a pressure imbalance between the hot and cold, causing the valve to restrict some flow. The restricted flow causes the on demand system to get hotter since it is using less (or, turn itself off because the flow rate is not sustained above the minimum). It can be a wild ride! Filling a tub is through an unrestricted tub spout, but when you switch to the shower, that flow may be cut in half or less because of the (again, federally mandated) low-flow restrictor in the showerhead. This can mess up the flow through the on-demand system, changing the temp. Now, most on-demand systems have at least some modulation and can compensate, but not all.

    What may work is to drop the temp on the on-demand system so you are using nearly all hot all the time, but then that may be insufficient for some other uses. It may be the only way to take a decent, safe shower with the system you have.

    While you can buy them some places, it is illegal to install a shower valve without the mandated anti-scald features. And, nobody would want a spurt of 120+ degree water coming out of the showerhead!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    janashusa has nailed it - its not the moen valve - it is the change in flow from tub spout to shower that causing the fluctuation... water going through the tub spout at say 10 gpm is going to "absorb" less heat on its way through the on-demand as it would when flowing at 1.5-2GPM through a shower head.

    there may be an issue with debris or something in the on-demand unit.

    I had a similar problem a little while back - the water would get just luke-warm on tub spout and very hot on shower head. there was a flow-restrictor in the on-demand that had failed and was allowing the water to flow through too fast to heat up sufficiently on tub spout function.

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    Moderator & Master Plumber hj's Avatar
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    quote; the 1222 valve has an anti-scald setting when it diverts water to the shower.

    The 1222 is a "cartridge" and it does NOT have any "anti scald setting", at least as far as temperature is concerned. It's antiscald function is "pressure balancing" but you can run ALL cold water, or ALL hot water, or ANY mixture in between. The shower head does have a flow limiter, but it is greater than the volume needed to operate your tankless heater. You have some other factor at work that you have not diagnosed yet. Your Moen "Engineers" are blowing smoke and have absolutely no idea what they are talking about relative to your problem.
    Licensed residential and commercial plumber

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    Quote Originally Posted by hj View Post
    quote; the 1222 valve has an anti-scald setting when it diverts water to the shower.

    The 1222 is a "cartridge" and it does NOT have any "anti scald setting", at least as far as temperature is concerned. It's antiscald function is "pressure balancing" but you can run ALL cold water, or ALL hot water, or ANY mixture in between. The shower head does have a flow limiter, but it is greater than the volume needed to operate your tankless heater. You have some other factor at work that you have not diagnosed yet. Your Moen "Engineers" are blowing smoke and have absolutely no idea what they are talking about relative to your problem.
    he may be referring to the 2pc plastic limiter included with the valve that can be set to "X high limit" temperature by limiting the rotation of the valve handle.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    That would have nothing to do with "when the water is diverted to the shower" which is what he said he was told.
    Licensed residential and commercial plumber

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    DIY Member WorthFlorida's Avatar
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    You may not need to tear out the surround if the wall behind the valve is accessible. Open up the wall and if you're good at it you change the valve body out but every here implies that any manufacture can have the problem. Have you called the water heater company? I'm sure they came across before and they may have a fix.

    In the mean time to get a good shower, try running the hot water at a sink or another bath tub to get a higher flow rate through the heater. It will diminish your savings on heating water and will prove that it is the anti scaling/demand heater combination is the cause.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Or maybe pick up a shower head that puts out more water.

    I know of one instance where the homeowner upped the temperature of a tankless to 140, and runs a Posi-Temp very well.
    I don't know if 120 would have been an issue with it.

    One thing I don't understand, is that the Posi-Temp is "pressure" balanced. It's not a thermostatic valve. The Moen doesn't care whether you have cold on both sides of the valve. All it does is dole out water based on pressure.

    So to me, it's get a splashier shower head, or tweak with the flow unit on the tankless.
    Last edited by Terry; 10-02-2013 at 05:52 PM.

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