tankless water heater heats water for about 5 seconds then stops

T

The motor guy

Joined
Nov 29, 2009
Messages
9,523
what does this mean? I was taking a shower and all of a sudden no hot water. Now it's definitely drawing power because the lights dim when you turn the hot water on, but it puts out hot water for about 5 seconds then no more hot water after that. I never bothered to flush it, wonder if I need to.
 
It's an eco smart 8 water heater

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Google the owners manual and follow their instructions on flushing the heater. How's the incoming water pressure? if not enough the unit will not heat or stop heating say if another faucet tap or toilet is flushed.

Flushing is usually a standard procedure 2-3 short hoses, transfer or sump pump 5 gallon bucket and distilled white vinegar or a descaling agent meant for flushing tankless water heaters.
 
Electric Point of use heaters are generally reliable. Not many moving parts. Beyond an anomalous electronic issue, the flow switch is likely the culprit.

Disconnect power, flush with white vinegar for 1 hour, retry.
 
burbguy82 said:
Electric Point of use heaters are generally reliable. Not many moving parts. Beyond an anomalous electronic issue, the flow switch is likely the culprit.

Disconnect power, flush with white vinegar for 1 hour, retry.
Click to expand...
The kitchen sink is also connected to it and it still gets plenty of water on hot, it's just not hot. I mean, it's drawing power it's just not heating. The outlet side is barely above room temp when I put my hand on it. I don't get why you cant backflush it though.
 
The motor guy said:
The kitchen sink is also connected to it and it still gets plenty of water on hot, it's just not hot. I mean, it's drawing power it's just not heating. The outlet side is barely above room temp when I put my hand on it. I don't get why you cant backflush it though.
Click to expand...
I understand.

Many of these units use a "wheel" for the machine to sense water flow. If the wheel does not spin, the unit will not turn on. Further the element could be in need of cleaning. The wheel not spinning will not reduce flow. If the sensor that tells the heater that water is moving is not working properly, the unit will not fire. This is the same on ALL tankless heaters. It is the starter switch so to speak. That and a safety to protect the heater.

If it is actually drawing proper power, it would be heating at least some. Just because it is on, does not mean it is heating.

Flushing is recommended once per year on any tankless heater by in large.

Some small tankless units are not really made to be serviceable which is to say that it would be unlikely that you would find a plumber who is willing to work on it as opposed to replace it. I would not, just for liability purposes.

Look on Youtube for a tankless flushing video and give it a shot.

BTW, I am a licensed plumber, whatever that is worth.

Edit:

To your question about back flushing.........not sure why this really matters as to flushing it, you have to disconnect the hoses anyway, but, some units have a check valve which stops back flow, for various reasons. There are too many different units and brands for me to be specific on yours, but generally, you flush them in the direction of flow, for 30 mins to an hour with a solution for tankless heaters, but most use white vinegar and distilled waters or just vinegar.
 
burbguy82 said:
I understand.

Many of these units use a "wheel" for the machine to sense water flow. If the wheel does not spin, the unit will not turn on. Further the element could be in need of cleaning. The wheel not spinning will not reduce flow. If the sensor that tells the heater that water is moving is not working properly, the unit will not fire. This is the same on ALL tankless heaters. It is the starter switch so to speak. That and a safety to protect the heater.

If it is actually drawing proper power, it would be heating at least some. Just because it is on, does not mean it is heating.

Flushing is recommended once per year on any tankless heater by in large.

Some small tankless units are not really made to be serviceable which is to say that it would be unlikely that you would find a plumber who is willing to work on it as opposed to replace it. I would not, just for liability purposes.

Look on Youtube for a tankless flushing video and give it a shot.

BTW, I am a licensed plumber, whatever that is worth.

Edit:

To your question about back flushing.........not sure why this really matters as to flushing it, you have to disconnect the hoses anyway, but, some units have a check valve which stops back flow, for various reasons. There are too many different units and brands for me to be specific on yours, but generally, you flush them in the direction of flow, for 30 mins to an hour with a solution for tankless heaters, but most use white vinegar and distilled waters or just vinegar.
Click to expand...
Yeah this thing is a small unit 8kw I think. It's only like $200. I thought these things were like $800 may just have to replace it if fillushing don't work. I need a shower before Thanksgiving dinner 😂
 
The motor guy said:
Yeah this thing is a small unit 8kw I think. It's only like $200. I thought these things were like $800 may just have to replace it if fillushing don't work. I need a shower before Thanksgiving dinner 😂
Click to expand...
Yeah, tech has made them cheaper, which is why servicing at this point might not be worth it. Sometimes it very scaled up, there can be issues. Best if serviced every year, not after 6 or whatever.

I generally take a shower once every 3 days if I am not doing anything. Wife likes the smell, or so she says. I think it is to act as an anti other woman mechanism. They lie. To much info there..... 🤬

Cold showers are good for the soul, not much else. Good luck
 
Sometimes mine will not heat water. Unplug it to reset sensors and board. Plug in and it heats again.
 
burbguy82 said:
Yeah, tech has made them cheaper, which is why servicing at this point might not be worth it. Sometimes it very scaled up, there can be issues. Best if serviced every year, not after 6 or whatever.

I generally take a shower once every 3 days if I am not doing anything. Wife likes the smell, or so she says. I think it is to act as an anti other woman mechanism. They lie. To much info there..... 🤬

Cold showers are good for the soul, not much else. Good luck
Click to expand...
I can't stand cold showers. We have well water so it's like 50 degrees
 
burbguy82 said:
Yeah, tech has made them cheaper, which is why servicing at this point might not be worth it. Sometimes it very scaled up, there can be issues. Best if serviced every year, not after 6 or whatever.

I generally take a shower once every 3 days if I am not doing anything. Wife likes the smell, or so she says. I think it is to act as an anti other woman mechanism. They lie. To much info there..... 🤬

Cold showers are good for the soul, not much else. Good luck
Click to expand...
They seem to stay around longer if they think you're the man all the other women want 😂 you've found the secret my friend.
 
walterjay said:
Plumber here.....yeah you gotta flush them usually once a year.
Click to expand...
I decided to tinker with it today. All I did is put my hand on the outlet side because I heard what sounded like maybe boiling water or pressurized water inside the unit. This thing is heating and the display that shows the water temp isn't even on. I put on hand on the outlet side and it was plenty hot. I don't think it knows when it's supposed to be on or off. I hadn't even used any water before this, I was at work all day. This isn't a dirty heating element, this is control board issue or something like that if there is one. I don't see where that wheel that monitors flow would come into play when I haven't used any water. I'm glad I caught this before I had $1,000 eletric bill.
 
I is likely a flow sensor if the element is getting hot. It’s still a good idea to flush it though. I’m surprised it hasn’t thrown any codes. These things usually do have diagnostic codes.

Edit:
I see it’s a point of use, so probably no diagnostic codes or anything like the hole house units.
 
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