plumbing or tankless water heater?

sybrashNovember 19, 2010

We have a Takagi tankless hot water heater (1st generation - I think it's a TK-1) A couple of months ago, we noticed that the water was not getting as hot as it used to. Previously, the water got so hot that you would actually have to turn it more to the cold side on occasions in order not to get burned. As it is now, you have to turn it all the way to hot to get it hot enough for a shower, but it is just hot enough. When you turn on the hot water only on the tub in 2 of our bathrooms, it starts to feel like it is heating up but after about 10 seconds it turns completely cold. In our master shower we have dual single handled shower heads and this is the only place we can get hot water - but like I said, just hot enough. We spent $150 on a svc call from a co recommended by Takagi as a certified tech. He said that there was nothing at all wrong with our water heater and recommended that we replace the mixing valves in our shower heads and said that should fix the problem. We spent $100 doing that (parts alone) and it didn't do a darn thing! We still cannot get any hot water in 2 of our bathrooms and water in the master not hot enough. Any suggestions? We've got $250 in this so far (could have put a regular water htr in for that price) and still no hot water! Oh, and it is operated on propane gas. HELP!

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Did this start with colder weather?

Incoming water temperatures change throughout the year.

In winter they are often lower (approaching 35F-40F in some places), and a tankless heater needs to have enough power (BTU/hour output) to overcome the lower starting temperature.

The above ground tanks used to supply operating pressure for a water system are not normally heated (and are buried if areas subject to deep freezing).

    Bookmark   November 20, 2010 at 10:00AM
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It sounds to me like the dip tube in your WH has failed.
It also sounds like your 'service tech' owes you a refund.

    Bookmark   November 20, 2010 at 12:35PM
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Randy, that was a clueless response, come on a dip tube in a Tankless water heater? Stick to recommending surgery procedures.

OP, TK -1's have water adjustment valves to regulate flow, that has failed, there is a thermistor issue or the board is bad, gas supply problem, or yes possibly a mixing happening outside of the unit itself, such as a shower valve.

Don't give up, sorry you may have gotten a poor service tech, keep looking and don't pay until he can prove to you what is really happening, not guessing

    Bookmark   November 20, 2010 at 7:21PM
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I believe these tankless units have .25 or .38 tubing for the coils. Have the tech check for sediment build up by over riding the burner control. Tankless units in boilers have this problem and .50 tubing is used in the heat exchanger

    Bookmark   December 1, 2010 at 11:18AM
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One thing zl700 didn't mention and jonnyp alludes to is- do you have moderately hard water, and has the unit been de-scaled?

It could be controls, but scaling buildup would eventually cause pressure drop and/or poor performance (detected by the onset of cold incoming water).

I don't know about the Takagi's, but the service mode on our Noritz has a bunch of data fields you can see on the display to tell how it's performing. I wrote a bunch down when troubleshooting directly with them early on. I would think there is enough info there to diagnose the problem, if the Takagi has a similar mode.

I'd ask for my money back from the original tech and find someone else or ask for a free followup.

    Bookmark   December 2, 2010 at 4:45PM
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I may be real late in answering the question but it sounds to me like you have a dirty burner tray and it has to be cleaned up. Did you do any maintamnce at all on this unit. They should be de-scaled every year, they also should be free of dust and dirt.

    Bookmark   December 12, 2010 at 1:18AM
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