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Tankless Water Heaters

Anybody have one?



8:27 pm on Nov 25, 2009 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

My wife and I are thinking of installing a gas tankless water heater to replace our 50-gallon electric model. The old one is actually working great and really doesn't need to be replaced, but we want the extra space for storage, and we figure the energy savings will pay for a tankless heater in about five years. But it's not exactly a small investment, so we don't want to do it if it's not going to work well.

So how about it? Does anyone here have experience with this sort of water heater? Pros? Cons? What should we look for? Will hot showers be a thing of the past? Other thoughts?

Thanks in advance,



8:38 pm on Nov 25, 2009 (gmt 0)

10+ Year Member

I started to go the tankless route a year ago and talked to a builder friend about them.

He said as long as you don't have a lot of minerals or iron they do save money but if you do have a harder type of water the heat plates gunk up quickly and need to be replaced.

If you think about how hot the heat plates have to get in order to heat the water as it flows past you can see the problem.

I still have the old heater in right now.


9:16 pm on Nov 25, 2009 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

Thanks Conard. I should have added that this will have a water softener behind it, so it will be getting pretty decent water.


9:29 pm on Nov 25, 2009 (gmt 0)

WebmasterWorld Senior Member billys is a WebmasterWorld Top Contributor of All Time 10+ Year Member

I'm thinking about getting one myself...

>>Will hot showers be a thing of the past?

I think you meant to say "cold" shower. You'll have a continuous supply of hot water.

These units are direct vent - meaning they go right outside the home - no chimney or you'll get condensate in the flue.


9:30 pm on Nov 25, 2009 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

Stayed at a friends earlier this year who has them.

I found it impossible to maintain a constant temp in the shower, which bugged me to no end.

Based on that experience I would use them at sinks only.


10:21 pm on Nov 25, 2009 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

I lived in an apartment in Korea with a common setup (common for Korea I mean)...

There was a little tankless natural gas water heater mounted on the wall in an unheated, enclosed balcony. This heater was connected to the shower via plastic tubing which ran three or four meters through a solid concrete wall that communicated with the building's exterior.

This meant that for the coldest month or so of the winter, the wall and the pipe through which the water traveled were so cold that the water just barely retained enough heat to come out of the shower somewhere between room and body temperature. Not exactly what you'd call 'hot'...

However, assuming you can avoid the very badly planned construction I described above, I think they're great. We had no hot water troubles in warm weather :)

-- b


12:27 pm on Nov 26, 2009 (gmt 0)

WebmasterWorld Senior Member kaled is a WebmasterWorld Top Contributor of All Time 10+ Year Member

I live in the UK - I think what you are referring to what we call a combi-boiler (provides instant hot water, zero storage of water and can also heat water circulated through radiators). In your case, it sounds like there are no radiators but the points should still apply.

Be aware that...

1) Even good quality heat exchangers typically last only about five years and can leak badly when they go wrong (so consider the location).
2) You should look for an efficiency of at least 90%.
3) You need about 10KW for a decent shower (7KW absolute minimum). That's heat output into the water not heat input which may include waste.
4) Your existing shower installation will need modification. Assuming it is a gravity/pump system right now, you will need new pipework and a pressure-balancing valve (name may be different in the US). This valve allows hot and cold water to be safely mixed to achieve a safe and stable temperature even when the mains water pressure changes.



12:37 pm on Nov 26, 2009 (gmt 0)

WebmasterWorld Administrator lawman is a WebmasterWorld Top Contributor of All Time 10+ Year Member Top Contributors Of The Month

When I was checking into them a few years back, they were not cost effective if powered by electricity. Don't know if that's changed.


1:49 pm on Nov 26, 2009 (gmt 0)

10+ Year Member

We have a combi boiler it was in the house when we bought it and we have plenty of hot water and no real problems.

About six months ago the water wouldn't heat up, we called out our local plumber who told us that the boiler was knackered and quoted us over 2000 for a replacement. We then called another Gas Safe registered plumber who told us the same. We were almost resigned to paying out for a new one when my wife contacted the makers of the boiler and they sent their authorised repairer round; he fixed it in about twenty minutes. It was sludge in the heat exchanger. We live in a hard water area. He told us that the boiler should give us another 10 years but on his advice we had a low cost electro magnetic anti scale device fitted on the water intake. This is apparently now mandatory on combi boiler installations.

The only downside I've found is that it takes a while for the hot water to come through on our upstairs shower and upstairs washbasin, and we are probably using more water than we should because of this. However the downstairs bathroom and the kitchen get hot water in just a few seconds, and the energy saving because we don't have to keep a big tank of water hot all the time more than compensates for the extra water used.


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