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Understanding tankless recirculating water heaters

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I was directed here from another forum. I have been having difficulty finding information to help me understand what has been happening with my tankless water heater.

When we moved into our new house. That has a Bradford and White tankless recirculating water heater. It seemed to work correctly for about 6 months. We were hearing about dozens of failing water heaters out of 70 new houses. FF to today they may have replaced as many as 36 of them maybe more. All similar issues primarily long wait times, inconsistent hot water temperature, I recently learned is called "cold water sandwich" others including ours a year ago suddenly get scalding hot water. At the time we were told we had a cracked solenoid. The builder's plumber replaced it under warranty.

We continued to have long wait times and other weird issues. Later the plumber told me that the problem is B&W came out with a improved model and installed 1000 of them, ours being one of them. Then they discovered a problem and updated the design and he has been a victim here because he has been having to replace them for free, eating the labor cost. He also told me when the heaters display on error code the unit can be replaced in a half an hour otherwise it takes hours to go through the diagnostic process to figure out what is happening.

So anybody with a error code gets a new water heater. Dozens, like us have the same basic issues but no code we have been told your warranty is up and you have to get it fixed on your own.

Our multiple issues one as far as I can tell is only at our house. The hot water is at the kitchen sink and the master bathroom is pretty consistent with occasional long waits a few times it was more than 8 -10 minutes having ice cold water. I ended up turning the unit off and on letting it recycle and was able to get hot water again. Often mostly if I get a shower at odd times during the day, say early afternoon after mowing the lawn. It will take a long time to get hot and I just get a cold shower and it warms up about half way through.

Here's the weird part that no one has been able to explain, neither plumber or the B&W Rep. In the 2nd and 3rd bathrooms the tub faucets when I turn them on "all" hot pretty much anytime but it may be worse in the morning. In seconds it's warm and suddenly it turns cold and stay cold. If I turn it off and back on within seconds it turns 90% hot only to turn cold again. This happens continuously, turning it off and back on again. Also in those bathrooms if you turn on both the sinks and tub one or both will turn completely cold. I have noticed that if several hot water valves are open it becomes warm possibly cold.

The builder's plumber was going to give me a new water heater but when he realized I had no codes and after showing him that scenario he stopped the replacement and said it must be the one of the 5 faucet cartridges in the house and that is part of home maintenance. Basically I'm on my own call a plumber.

So I did. He seemed like a knowledgeable guy and he over two different days diagnosed and came up with a few possibilities. He changed the 2nd and 3rd bathroom tub cartridges, changed a 1/2 inch flexible gas line to a 3/4 and fixed a better option for the intake PVC pipe.

Now I'm up to $595.00 and nothing is fixed. The plumber I hired also had the rep come and look at it during the 2nd day of work. I told him about the dozens that I'm aware of that have either been replaced or are still having problems. Last I talked to my plumber he was also suggesting that maybe the hot and cold water hoses got crossed but that is only a guess. He said he knows the builders plumber and would have to consult with him to try and figure out what might be going on.

Because it seemed to work normally for the first 6 months I don't think it was plumbed wrong. I think something is wrong with the water heater and because of how it was plumbed the 2nd and 3rd bathrooms react differently than the kitchen sink and master bathroom.

But really I have no idea what or how much it will cost to just blindly try and fix this.

I have learned for the most part how to live with it. If you run the 2nd and 3rd bathroom sinks hot for a few minutes then take a shower the temperature stays a constant 90% hot never 100%. I also turned the temperature up to 125deg and all hot at the kitchen is near scalding once in a while but never in the the bathrooms and certainly not in the secondary bathrooms.

Sorry for the long text and hopefully someone will have some answers for my complex issues.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,746
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    If it was mine I would toss it out and install a tank type water heater. Some will recommend a heat pump water heater, but they have their own issues, and I am sure you are sick of water heater issues.

    I agree with you that if it worked right for the first 6 months the plumbing is likely ok but a faulty cartridge could cause some strange issues. Maybe @Larry Weingarten and others will have some ideas.

    Larry WeingartenMad Dog_2
  • pedmec
    pedmec Member Posts: 994
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    Did they check the temperature of the hot water leaving the water heater to confirm that the water heater is causing the issue. just because you have hot water issues doesn't always mean its the water heater. you need to narrow down your search

    Does your hot water system have a recirculation line?

    Ghost_Rider357
  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    I think now that the has been plumbed for a circulating system it would be costly to convert it to a tanked noncirculating system plus the length of time to get warm then hot water would become annoying. On the plus side we already set it to circulate 6am to 10pm and the most of the time the water in the pipes is around 50-70% hot sometimes often taking 30+ seconds to get that warm. If I had to I can live with this. The biggest problem is when we have guests we have to tell them to run the sink hot water first. I have recently showered in these and it seems to work but never more than 90% hot, but warm enough.

  • Larry Weingarten
    Larry Weingarten Member Posts: 3,356
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    Hi, Some thoughts. We need to see if the problem is with the heater, the plumbing, or both. A good test of the plumbing is to shut off water to the heater and then open any hot tap. Does water stop running in a few seconds? If it keeps running, there is a crossover between hot and cold which needs to be fixed. Is there a tempering valve?
    About recirculation: is there a separate pump for moving water through the hot plumbing? Can you give us some photos of the heater and connecting plumbing? If there is a recirculating system and if it isn't done right, it could be a big part of the problem. Just for your information, it's hard to get recirculation to work well with tankless heaters for multiple reasons. Recirc can work just fine with a tank.
    I'm guessing your heater has a screen at the inlet. Screens get dirty, slowing flow, and this can make the heater very unhappy, which it will be sure to let you know. Has the screen been cleaned recently?
    Yours, Larry

    Ghost_Rider357
  • Jamie Hall
    Jamie Hall Member Posts: 23,543
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    I think I need to see a diagram of the plumbing involved here. Without that, I — at least — would find it hard to pinpoint the problem.

    Other than a rather fundamental problem: tankless water heaters and recirculation systems are contradictory. The whole concept of the tankless is to take the flow to the hot water fixture or fixtures and, with a very large power source, heat it from a cold source to hot as it passes through the heater. The whole concept of the recirculation system is take a source of hot water — a tank full of it — and recirculate it slowly through the hot water (and return) pipes, so the water in the pipes is always hot, and hot water is available at the tap immediately. There is a low power source in the tank to reheat the tank from time to time to keep it in the desired temperature range.

    They don't mix.

    In the meantime, is there a check valve on the return line for the recirculation?

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Ghost_Rider357Mad Dog_2Larry Weingarten
  • DCContrarian
    DCContrarian Member Posts: 200
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    "Other than a rather fundamental problem: tankless water heaters and recirculation systems are contradictory."

    That was my first thought when I read the thread. I bet if you read the manual for the heater it specifically says not to try to run it with a circulator.

    How about putting a 5-gallon electric tank downstream of the tankless? Run the recirculation into the small tank, let it handle the standby losses, the tankless only runs when there is real demand for hot water. It would probably help even out the temperature output of the tankless as well.

    Call it "semi-tankless."

    Ghost_Rider357HomerJSmith
  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    Thanks Larry,

    This is very good information. Are you suggesting that I turn off both the heater and the inlet valve, shown in the picture? I'm pretty sure that just powering it down will not stop the the water flow. Turning both off sounds like a very good test. Even a rookie mistake that none of the plumbers or the company rep knew.

    I will say this, the homes that had replacements are no longer having issues.

    The other two pictures are in a chase, that I have access to. You can see multiple hot and cold lines coming up from the slab. Hot on one side cold the other. All of these directly to all 3 sinks and one of the tubs for the 2nd and 3rd bathrooms.

    I have lots of pictures during construction showing the water hoses.

  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    The specific water heater is a Bradford and White Infiniti tankless L-series model RTGL199N1 the recirculating pump is built into the unit.

  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    Assuming that the two tub cartridges I replaced are good. Should I consider taking the 2 original cartridges and replace two of three in the master shower?

  • Jamie Hall
    Jamie Hall Member Posts: 23,543
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    I presume you have the manual for the appliance? If not, it's here.

    Go through it with a fine tooth comb. Make sur3e that the installation is complete and correct. Make sure that the check valve (if this is a dedicated mode recirculation system) is correct, in place, and working. If this is a bypass mode system, check that the bypass valves are working correctly.

    There is a pretty extensive trouble shooting section. Go through that with an open mind…

    https://bradfordwhitecorp.s3.amazonaws.com/wp-content/uploads/residential_tankless_infiniti_L_n1_iomanual_827_274.pdf

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Ghost_Rider357Larry Weingarten
  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
    edited June 10
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    Now we are getting somewhere!!!

    Thanks for suggesting going through the manual. When I shut off the cold water intake to the water heater I went around and checked all the hot water valves. The kitchen sink, laundry room sink, 2nd and 3rd bathrooms all had a few seconds of drips and stopped as did the sinks in the master bathroom. In the master shower all 3 have continuous drips and no cold water either. Just verified that all 5 tub/shower valves don't have cold water either, not in the normal way. The sinks all have normal cold water and nothing but a few drips of hot.

    Again makes me wonder are these rookie mistakes how did neither plumber or the B &W rep not know this test.

    I think that my next test is to replace each cartridge in the master bathroom one at a time. Then preform the same test looking for difference.

    The picture of the shower shows the valves all 3 bathrooms have and that all 3 in the picture are dripping continuously.

  • DCContrarian
    DCContrarian Member Posts: 200
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    "In the master shower all 3 have continuous drips and no cold water either. Just verified that all 5 tub/shower valves don't have cold water either, not in the normal way. "

    I would expect that the shower valves are pressure-balanced to prevent scalding. So when the hot water is off there would be at most a small trickle of cold water.

    Ghost_Rider357
  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    In 2nd and 3rd bathrooms it's just a few drops. What I meant when I said normal way is, in these bathrooms when I turn the valve to cold I can get a spert of cold then it stops. In the master all 3 just keep dripping pretty much the same whether they are all hot or a mixture of cold.

    That sounds like the pressure balance you are talking about. Still the master shower is different than the other two bathrooms. So that's pointing to it being the problem. The house is only 18 months old so is it worth changing the 3 cartridges in the master, perhaps with new. Or does swapping them one at a time using the ones from the other two bathrooms a more sensible start?

  • DCContrarian
    DCContrarian Member Posts: 200
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    I still don't understand your description. What problem do you think is happening, and how do you think changing the cartridge will fix it?

    HomerJSmith
  • HomerJSmith
    HomerJSmith Member Posts: 2,477
    edited June 10
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    If the unit worked correctly for six months, I would suspect it is the heater and not the cartridges. Of course, water quality can make a difference in cartridge performance.

    When I have situation such as your, I will routinely look at the electrical. I will disconnect all plugs and receptacles and spray them with Electronic Cleaner that you can get at Walmart or any auto parts store.

    I then reconnect them while still wet with cleaner. Do this with no power to the unit and one connector at a time. This includes the circuit board. It's surprising how this will many times return a unit back to correct functioning. Try it what have you got to lose, six bucks and a little time.

    As an added note, I have had this kind of problem with the HTP Munchkin boiler's Molex connectors to the circuit board and I replaced the offending Molex female connector to the circuit board pin with a new one which corrected the problem. I can't tell you why the offending Molex connector wouldn't pass the current to the pin but it solved the problem.

  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    I have been told by the plumbers that sometimes the cartridges fail and allow the cold water to mix with the hot. I would want to change them to rule out that they are not causing the water to bleed through.

    Because according to the manual the master shower should not have cold bleeding through. Suggesting that I have a crossed pipe.

    I said it was working normally for 6 months. The fact is that we rarely used those bathrooms so who knows for sure.

    The other thing is the long wait times that happens at odd times during the day.

  • hot_rod
    hot_rod Member Posts: 22,353
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    It takes a minimum amount of flow for the units to trigger on and heat consistently. Could the shower heads be too restrictive? A partially plugged inlet stainer can cause these issues also.

    What is the water pressure in the home?

    Is there a thermostatic mixing valve in or on the hot outlet of them heater?

    Tub shower valves can be pressure balance or temperature and pressure balance type. If you have hard water the cartridges may need routine cleaning to keep them working accurately.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    HomerJSmithGhost_Rider357
  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
    edited June 11
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    I'm hopeful that at least one of my water heater issues is fixed.

    I already paid the my plumber to replace 2 cartridges, part of the $595.

    Nothing improved so you would think the 2 original cartridges are good. I contacted the builder's plumber he was adamant that the it is a bad cartridge not a crossover. He told me a way to tell which cartridge might be bad being correct 90% of the time.

    It didn't work for me but I changed out 2 of 3 in the master shower and just by chance the 2nd total of 4 have now been changed or switched.

    Huge improvement in the temperature in the 2nd and 3rd bathrooms. Starts out warm within seconds it starts getting hot and for the first time it starts getting uncomfortably hot. I have it set to 125 degrees.

    However I redid the test I found in the manual I posted yesterday and the master shower appears to keep dripping indefinitely.

    It will take a couple of days to make a judgement but I'm hoping it's fixed.

  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
    edited June 12
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    It's looking like things are definitely improving. Talking with a friend and other posts I've read makes me think this is a case of the effects of hard water. A friend that's been living in the area for a while told me about a house annually he to soak the cartridges in vinegar. He said it's a good idea to turn the water back on with the cartridge removed to clear the line out.

    That makes sense in a way because it's one of two valves we use daily. I'm going to change the 5 valve cartridge. That's the one my wife uses mostly. Then soak both cartridges in vinegar and put them up and wait till things get wacky again.

  • hot_rod
    hot_rod Member Posts: 22,353
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    I know of cases where thermostatic mixing valves need deliming every 6 months. Same with tankless heaters.

    It depends on how hard the water is, how hot you run the heater, and how much water passes through the valve.

    Maybe consider a water softener on the hot, or one of the other water conditioning methods, TAC for example.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Ghost_Rider357
  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    I spoke to soon a day later it seems to be the same as before. It boggles my mind how this is happening.

    Why does it seem to work at different times of the day? It seems that in the morning I turn on one of the secondary bathroom tubs the temperature is warm then turns cold and stays cold for a long time several minutes if I leave it alone. When I turn the valve off then back on I get a blast of hot water and then it turns cold again. If I run the sink first then the the tub it works better.

    It seems like there is a crossover, mistake by the builder's plumber. He refuses to think that is possible. He still says it's a cartridge. I've changed 2 rotated the other 3 and I still have the same issues.

    So my three choices are, spent 4K and get a new water heater and maybe nothing will change because it's plumbed wrong, spent thousands to do forensic research to try and figure out what was plumbed wrong, or I can just live with a f***d up system.

    Eventually I will have to replace the water heater sooner or later. I could wait until then but if I wait till then I won't be able to take the builder or his plumber to court. Something I'm not sure I'm up I did speak with a lawyer and make no mistake would be an up hill climb costing thousands and even if I win might not recover legal costs.

  • DCContrarian
    DCContrarian Member Posts: 200
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    Do your shower valves have stop valves in them? Valves that shut off the water so you can work on it without turning off the house water? Usually they're part of the valve body and turn with a flat-head screwdriver.

    Crossover between hot and cold water can cause a lot of mysterious behavior and can be tricky to find. If you shut off the hot and open a tap you should be able to see if crossover is happening, water comes out of the hot. Sometimes it only happens when a fixture is on, using the stop valves allows you to isolate shower valves.

    Could it also be that the water heater is working fine, and the problem is with the mixing valve in the shower?

  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    I don't think there are any shut offs. They are Delta valves and I saw no screw adjustment from the front when I was swapping cartridges. There are shut offs for the sinks and toilets but no access to tubs and shower.

  • DCContrarian
    DCContrarian Member Posts: 200
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    OK, try this: shut off the hot water. Open the valve in the shower so cold water runs out. Go to a sink and open the hot faucet. Do you get anything? Try that with each shower, one at a time. Then look at every fixture in the house that mixes hot and cold, and check them too — washing machine, tubs, etc.

    Are your shower valves thermostatic? I find they tend to be more troublesome.

    What you want to be thinking about is diagnosing the problem, which starts with getting a grasp on the symptoms. Keep a thermometer by the sink in your shower. Measure your hot and cold water temperatures at the sink to get a feel for what normal temperatures look like. When the shower starts acting up, leave the shower running, go to the sink and measure the temperatures. That might give you a glimpse of what's going on.

    At this point the question is whether it's just the shower mixing valve acting up, or the whole hot water system.

    Ghost_Rider357
  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
    edited June 14
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    Your suggestion is similar to the test in the manual I posted back a few posts.

    Turn off the hot water and open all the hot water valves in the house. Check them in 10 minutes. Any continued drips large or small indicates a plumbing crossover.

    My results are only the 3 master shower valves all continue to drip. Every other valve stopped dripping in seconds.

    So where do I go from here? No plumber so far has been able to definitely tell me what is wrong. I can predict how that's going to play out. "Which valve do you want me to replace" eenie meenie miney moe

  • Ghost_Rider357
    Ghost_Rider357 Member Posts: 14
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    I doubt that the valves are thermostatic my builder was cheap. Gave the illusion of high quality but the subs were horrible.