0

I live in an 8 year old apt complex with a tankless water heater which is connected to a Viega water distribution manifold. I can't find them on the web anymore so they may have gone out of business.

This problem started about two years ago and has progressed very slowly. The hot water turns cold after about two minutes unless hot water is running elsewhere. For example, if I run the hot water in the bathroom sink, my shower water stays hot the entire time. If I do not run the water in the sink, the shower turns cold in two minutes, I have to turn the water off and wait about two minutes to turn it on and it will be hot again.

Happens every day. Kitchen sink does the same thing. Now the dishwasher is doing it because it used to work perfectly and now the dishes are still dirty. I did an experiment by leaving the hot water running in the sink the entire time the dishwasher was on (and that is a LONG time) and the dishes came out great.

I am very uncomfortable wasting so much water. I do not pay for the water but I believe it is precious. Anyway, my super has been working with the mfr of the tankless heater and has cleaned filters, removed slow flow devices, run white vinegar through the heater, nothing changes. I am wondering if the manifold has filters which need to be cleaned or if there is some other maintenance that needs to be performed.

Thanks.

  • Weird problem, yes. But not too hard to find the company on the web, for one thing: viega.us/en/products/innovations/viega-pureflow-pex-system.html – Ecnerwal Dec 16 '17 at 18:17
  • 1
    Sounds like a bad flow sensor on the tankless water heater. – Tyson Dec 16 '17 at 18:54
  • This might be relevant if the tankless hot water heater turns off if the flow of hot water is really slow, so: Do you have a low flow shower head? Because I have a low flow shower head AND a valve so I turn down the shower really low. – Bulrush Sep 9 at 11:18
2

Tyson sounds right on the money to me. However keep in mind that these on-demand water heaters require regular service. They must be acid washed regularly depending on how hard your water is to keep the calcium build-up at bay. As the calcium starts to build-up on the inside of the heat exchanger tubing, it insulates the water from the wall of the tubing. As this happens the sensors will have a more and more difficult time sensing actual water temperature.

0

This might be relevant if the tankless hot water heater turns off if the flow of hot water is really slow, so: Do you have a low flow shower head? Because I have a low flow shower head AND a valve so I turn down the shower really low.

Also, running vinegar through the system to remove mineral buildup is often not enough. My actual experience shows that to remove minerals may require a soak in vinegar for 8 hours, and several repetitions of this. In my case, I was removing minerals from a clogged chromed shower head. Any stronger acids (in my case) might very well damage the finish.

And for additional experience, I used to have a house that had water with high mineral content and we had a water distiller. Vinegar didn't work that well, to clean that thing I used a wire brush to get most of the minerals out, then an 8 hour soak in vinegar, rinse and repeat until minerals are gone.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.