OT Tankless water heater woes

I cant get the water to stay hot for more than 2mins in the shower. It will get hot and stay hot for two minutes and then get cold for 2-4 mins and repeat.
I had a plumber over and he messed with the knobs some and he said these tankless water heater are just like this. But all I read about them is that they give an endless hot water supply...
But nothing. Im thinking of just getting a tank.

More info.
Plumber said i would have more success eliminating my hot and cold knobs and joining them.
Water gets cold too if another water source is used.
I dont have a water presure regulator.

 

I have an electric one, and have not had any issues.

 

Are you turning the water on and off, or leaving it running?
The tankless heaters only heat when the water is flowing. If you turn it off and on again, you'll get some cold water until the heater heats up again.

 

Check the sediment filter/screen on the inlet line. if it gets restricted the heater will do exactly what you are describing.

 

Im keeping it on.

But i can hear the flame go off and on when someone else is in the shower.

 

Im going to look into that.

 

I thought the filter was to be here on the cold water supply? But i dont see one.

I tried unloading pictures but they say they are to large but if you see my 1st picture the pipe on the right. I opened up where the brass fitting goes into the aluminum pipe and saw nothing. I also seen a small orange thick residue in side the fitting.

 

Hold up im going go higher i seen a screen

 

Check the screens on the washing machine too; actually replace the hoses too while yer in there! A blow out can make a real mess FAST! ws

 

If you live in an area with a lot of minerals in the water these heaters won’t last very long at all. I have a plumber friend who says the supply shop he uses has a 3 foot pile of these that were ruined by water with high mineral content. Says a water softener helps. This might be a factor.

 

Yeah no filter, but i cleaned out the junk feom around the screen.

 

Ill do that

 

Saying "they just do that" is total B.S.

They have been selling these for years with millions (?) of satisfied customers. Everyone I know who has one loves it.

I know the hard-water issue exists, and the on-off-on issue exists. (My 10-15 year old electric unit does it after 15 to 20 minutes; I assume the sensor is going.)

Anyway, from an on-line article:

TANKLESS WATER HEATERS ARE NOT IMMUNE TO PROBLEMS
This is especially true if they are not professionally installed—in many cases, gas lines need to be extended in order to accommodate for an on-demand (tankless) water heater. In all cases, tankless water heaters must be property vented. If neither of these factors are properly addressed, then the tankless water heater might not be able to meet the demand being placed on it and will fail to work, as its computer system will be overloaded.


Another problem that tankless water heaters can run into is that of a cold water sandwich—a plumbing term given to sudden temperature fluctuations, when your tankless water heater produces hot and cold water intermittently. This can be caused by:

• An improperly sized gas line, as mentioned above.
• A plumbing system crossover where there shouldn’t be one.
• Improperly lengthened venting pipes.
• Damaged flow sensor—something that should be checked during your annual plumbing maintenance appointment.
• A dirty water filter on the cold water inlet.
• Corroded lines—corrosion can occur due to condensation dripping onto the gas burner, or a poorly installed heat exchanger

Full disclosure: Not a plumber, just looked into it before and decided 15-20 minutes was okay for my unit. 2 minutes seems unacceptable.
(Insert wife joke here.)

 

We have a tankless water heater as well as 2 boilers (tankless on demands) and I heard & read about all the problems they have with corrosion and such. We have a water softener, but still they tend to corrode up inside. I was @ the local home improvement store one day looking @ hot water heaters and seen these: https://www.menards.com/main/plumbi...68-c-8689.htm?tid=-4950853044712429890&ipos=4 and I bought a set for each unit.

With that valve set up I can easily clean the insides of each unit. I close the main valves, then remove the 2 covers on the pet cock valves, use an old set of washing machine hoses attached to the 2 valves, attach the inlet hose to a sump pump sitting in a 5 gallon pail, drop the end of the return hose into the pail and fill the pail with water and Iron Out or CLR or both and circulate that with the unit heating the water up. 5-15 minutes of circulation should be ample time to clean it good.

I do this 1 time a year with each unit, now going on 5 years or so and we have had NO issues so far.

I'd try this 1st before doing anything else, cause obviously you have some corrosion built up inside somewhere I'd bet or else your unit would work flawlessly.

I take 20-30 minute showers and NEVER have an issue, NO "cold water sandwiches" or anything like that.


Keith

 

I always replace the rubber ones with the stainless braided type . Costs just a few
bucks more.

 

Thanks for digging that article up for me. The plumber was full of it, i could tell. Then I looked his company up online and one star review with a bunch of unsatisfied customers. But whatever, Im going to call my home warrenty eventually and tell them.
Appricate it

 

Kieith thanks when I get the time tomorrow ill flush my system with clr. Thanks for the explanation, Ill do it just as you said.
Big thanks

 

Thanks I was going to get rubber ones

 

Looked into it and the water does have alot of minerals in it around here

 

Thanks Bill, send over your phone number again i lost it