About 16 years ago we elected to install a Rinnai tankless water heater which I talk about in this blog post.
No Problems Whatsoever. We have never had to have the water heater repaired and we use it, as any family does, ALL the time.
Cold Water Sandwich Effect is a Myth. At least it is for us. I have to say that I have never encountered this issue. All of my hot water pipes run through the cement slab that forms the foundation of my house. Those pipes must be piteously insulated because the water between the heater and the faucet cools at an extraordinary rate. Some people have tried to claim that this is the cold water sandwich effect, but it obviously is not. We had this issue of needing to run the hot water for a while for the 10 years we had old-fashioned tank water heater so it’s not a new thing. I do not find that, when restarting, ANY cold water sneaks through the tankless heater as I cycle it on and off.
Use the hot water normally. A concern I had when I first started using this technology, was that there were a lot of moving parts: Solenoids controlling water flow, valves controlling gas flow, and a blower fan. Even the parts shared with tank water heaters such as gas valves, are used much more often and frequently when the tankless unit is in use. I decided to just use the heater normally without consideration for this difference. I figured that, if this caused a problem, I’d just have to get it repaired and then change how I approach using the heater. After 16 years, I am amazed at how robust it has been and I have absolutely no qualms about continuing to use it normally and not worry about the mechanics of my heater.
Get a Thermo-Balanced faucet. For temperature-sensitive applications such as a shower where a swing in temperature might be unpleasant. This applies regardless of whether you have a tankless or tank water heater. When there is strong demand for either hot or cold water – such as a clothes washing machine, a toilet flushing or someone else taking a shower in your house – it can can change the pressure of one of the hot or cold supplies and leave you with a brief temperature swing. We are fortunate in that our water pressure is ample so that toilet flushing does not affect anything, but someone else starting another shower *can* have an effect. Basically the Thermo-balanced faucet will instantly (and I do mean instantly) alter the pressure for the other water supply to maintain the temperature. The net effect is that the overall pressure coming out of the shower will shift a bit but the temperature stays spot-on and comfortable.
Plan ahead if you want to recirculate. A number of years ago I heard about using a recirculating pump that I could add to my hot water system which, in conjunction with temperature-activated valves at the faucets of my choice, would ensure that the water at those faucets would be hot and ready to go instantly. The problem I faced was that I needed to find a recirculating pump that operated with enough force to trigger the Rinnai heater. This did not work out for me at the time. There are now tankless heaters with this kind of pump built-in. So if you want this kind of luxury, make sure your tankless heater supports it.
Do the Annual Maintenance yourself. There is only one maintenance task that is needed for my water heater, that’s to annually cycle 4 gallons of white vinegar through it to clear out scale from the coils and valves. The initial outlay is for a 5-gallon bucket from Home Depot, a pair of hoses (the kind you use to connect a clothes washing machine), and a small submersible pump (I purchased mine from Amazon for about $62 – Simer 2305 Geyser II 1/6 HP Submersible Utility Pump). I’ve performed this task faithfully starting about 3 years after the heater was installed. It takes about 90 minutes on a rainy weekend day and is VERY satisfying to clear tout the gunk that accumulates over a year.
Would I do it again? Absolutely, when the time comes, or if I move to a new place, a tankless water heater will certainly be part of my setup.