Please, help? Hot water only works with two faucets on?

[atleastmytearsarewarm]

Hello, can you please help me?
A little over a year now, my husband and I moved into an older, tiny home.
There's well water that's freezing all year long, pumped into the house via a water pump in the shop right beside the house. There's a tankless water heater in the front (not far from the bathroom, laundry, or kitchen since everything's close due to the small space).

Now, the problem is that to have hot water running in the shower, bathroom tap, or kitchen there needs to be two faucets running at the same time. To take a shower, we turn on the shower tap and the bathroom sink faucet and adjust the temperature there (it oscillates between scorching hot and freezing cold). To wash dishes in the kitchen, I have to turn on the bathroom faucet. As you can imagine, it's been really annoying, and I have burned my hands and frozen them too many times while doing the dishes.

We've tried a few things, but are completely clueless as to what could be causing the issue. Please, can someone shed light on what may be the issue?

 

[RS]

It sounds like your not getting enough flow to turn on the heater, maybe that is adjustable. Or else you could get a higher flow shower head. The best solution is to get rid of the tankless heater, and install a 20 gallon tank type, if the house is small that should be more than adequate. Or, you could leave the tankless in and put a tank type downstream from it, that's what one of my neighbors did. Every time I read one of these threads I'm glad I never installed a tankless! If you have to call a service man every time there's a problem you spend way more on service calls than you ever save on energy!

 

[wpns]

Has it always done this? Various types of tankless heaters work in different ways, but there’s a certain minimum flow to turn them on (and then the good ones modulate their output to keep a constant temperature output) which sounds like your first problem.

While OPlusPlumbing’s offer to drive 3200km to take a look at it is nice, you probably want to find a local plumber.

I’m with RS here, a small tank will give much better service than trying to diagnose and then replace your tankless.

 

[frontporch]

If you are truly in a tiny house you probably don’t have much space even for the smallest hot water heater but if it’s a very small house I would follow their advice

I don’t own tankless but I have heard they need yearly service/cleaning and maybe that is something worth investigating.

Can you provide pictures that identify the heater?

I would think that you shower and cook with the same amount of water as everyone else so I am skeptical about flow rate although the symptoms indicate that may be the issue

 

[wpns]

So obviously flow rate isn't hitting the minimum without extra faucets open, it's anyone's guess if that's relates to bad sensor or (as per OPlusPlumbing's reply above) low water pressure, so that's the first problem.

Your well has a bunch of pieces that interact with each other (pump, switch, pressure tank) that _could_ drive your tankless heater nuts, but if the water pressure seems fairly constant without any spikes or dropouts, then I'd wait to go down that rathole.

The second problem is the modulation of the power to the heater (is this natural gas, propane or electric?), which is either on-off (older units used to work this way, and had really poor control over output temperature) or some kind of proportional control which is acting up, or (see above) the minimum-flow sensor is flakey and cuts heater power in and out.

But yeah, answers to the questions above and pictures of the unit will definitely help with the quality of the advice you get. 8*)

Also, cue @Valveman if you need to save space by reducing the size of your pressure tank to fit a small tank heater.

And just be aware that tiny tanks can be frustrating in their own way, and apartment I had with a tiny heater would run out whenever I used it for anything, so I had to take a shower, wait hours for the recharge, clean the house, wait hours for the recharge, do the dishes, wait hours for the recharge, etc.

 

[Valveman]

Thanks for the mention wpns. Many times it is just the well or booster pump cycling on and off, causing the pressure to go up and down, which makes the instant heater turn on and off. Just adding a Cycle Stop Valve to the pump system in the shop maybe all that is needed to solve your problem. Instead of the pump continually coming on at 30 and off at 50 PSI, the CSV would keep the pressure at a constant 40 PSI as long as your shower uses more than 1 GPM. I am guessing the pump in the shop already has a small pressure tank, which is why it is cycling on and off so much. The small tank is all that is needed with the CSV and the CSV will hold the pressure strong and constant, keeping the flow through the instant heater constant, so sit will stay on. If your shower doesn't put out at least 1 GPM you can remove or drill out the water saver washer in the shower head to get more flow.

https://cyclestopvalves.com/collections/pump-control-valves/products/csv1a

 

[Bird Doo Head]

On the chance your heater is Rinnai:

Does your heater have an error code showing on the circuit board when one faucet is open? If so, an error code chart will pinpoint the problem. The code charts are available on line & at Rinnai.us. Some had the code display on the front of the unit, but for others you have to remove the front panel to see the circuit board.

At RInnai tech school we learned that when there is a little bit of lime build up, some of the early Rinnai had problems with a single faucet triggering the flow sensor that allows the burner to come on.
The initial repair attempt, per what OPlusPlumbing said in the first reply, is flushing. The procedure is simple and is outlined in the owner's manual. The manual for your unit will be available at rinnai.us under "Support".

Excess air in the water can also cause the flow switch not to trigger. If you well tank lost its air cushion, excess air could be the problem.

In case yours isn't a Rinnai, I would imagine all brands have some sort of similar diagnostic procedure.

I hope this helps you figure out the problem and solve it easily!
Paul

 

[atleastmytearsarewarm]

Thank you all so much for your answers. I am blown away with your generosity and willingness to help. I will study the responses, try some things and follow up.

I've attached photos of the heater manual. It's gas and was already here when we moved in, so we don't know if it's always done that. We've changed the filter, tried a few things, but the biggest thing that was eating away at me was having no idea what to even research! I tried a few plumbers, but they're too busy to come out and look (they've literally told me that), so before pushing for someone to come, I wanted to at least have an idea of what the issue is.

Extra info/answers:
- our house is about 400sqft and the heater is right at the front door, a few feet away from the faucets;
- the washing machine is right next to it, and interestingly enough, the washer triggers enough hot water without any additional faucets being turned one. If the washer's pulling hot water, all other taps will go cold;
- we installed new faucets (bathtub, kitchen, shower head, and disconnected the bathroom tap to remove the sink/vanity) right after we moved in. Not sure if that could alter anything.

Thank you again for all your help!

 

[wpns]

OK, so it looks like it's _supposed_ to modulate both the water volume and the gas volume in order to keep the temperature under control, if there's more to the manual that tells you how that should work and what kinds of troubleshooting is available you should refer to that.

Someone with more experience with tankless would be able to tell you what temperature rise a 74.5KBTU heater can provide if it's working properly, and you can go from there.

Has it always done this, or is the problem new?

 

[Bird Doo Head]

In the few instances that I've used it, Eccotemp has had very helpful diagnostic support. I'm confident that they can help you troubleshoot. I'm also confident that the problem will be easy for you to rectify, as Eccotemp are easily serviced units. Note, however, that my experience with Eccotemp has been limited to "off label" use (hydronic heating loops), not domestic water.

To speak to a technician on the phone, you have to go on line to eccotemp.com and create a Support Ticket for a call back from a technician. They let you schedule a call back time while you are booking the appointment. (Note that the site is ecCotemp.com, with two C's)

Or, you can also send an e-mail with your symptoms. Include the model & serial number. I think they also have live chat, but I am not positive.

When you book the call, send photos of the installation, the serial number and any error codes. It'll help them diagnose. (If I remember correctly, the error code will be on the front panel, near the bottom.)

The manual has a good troubleshooting chart and an Error Code chart that may help you figure this out. They also sell a descaler kit called "EZ Flush" for removing lime build up.

Hope This Helps!
Paul

 

[Taddpole808]

Did you ever figure out the issue? I have the same thing happening. Single faucet throws error 12. Multiple faucets hot water works fine. Bath tub by itself works fine as well. I haven’t flushed it in a year which is what I’ll do next.

 

[atleastmytearsarewarm]

Did you ever figure out the issue? I have the same thing happening. Single faucet throws error 12. Multiple faucets hot water works fine. Bath tub by itself works fine as well. I haven’t flushed it in a year which is what I’ll do next.

Nope; I reached out to Eccotemp as suggested. They said to flush it (hope it works for you!), but that didn't do much for us. Maybe a little difference in that now we can at least regulate the water to be warm (we used to either take hot or cold showers), but I also don't know how much that has to do with the temperature changes outside. It's worse in winter. Hopefully we get it fixed before then.

Hoping I can come back and update this with good news soon!

 

[atleastmytearsarewarm]

Did you ever figure out the issue? I have the same thing happening. Single faucet throws error 12. Multiple faucets hot water works fine. Bath tub by itself works fine as well. I haven’t flushed it in a year which is what I’ll do next.

Hi all, a plumber came in on Friday.

The tankless water heater is toast. Eccotemp's customer service made us flush, pushing their flushing kit on us. That didn't work, so they said I had to buy the valve. I did, and we switched it out. Things just got worse. We wasted so much time. The plumber came in and had one look (the same view I sent to Eccotemp through photos) and said it was obvious that it was done for and probably had been for a while. I am disappointed they made me buy parts. If you're having the same issue, I'm sorry, but you might need to replace your water heater. Just don't opt for an Eccotemp one.
Thanks for all the input from the community. Appreciated it.

 

[Bird Doo Head]

Thank You, atleastmytearsarewarm, for the update about Eccotemp. They used to be very helpful. It's sad that they spent your money for no gain. Hopefully your next heater, whatever brand, gives you premium service for years. (For all of them- Flushing on schedule is important.)
Paul

 

[richardmeyers1987]

Not enough flow.