On demand water heater

1. We currently have a  Rinnaiand in our last home we had one. Our last home was new, when we bought it, so the builder installed it along with PEX. First time that I looked in the attic and saw all that plastic PEX going every which way, I just thought of the possibility of a leak. Our current unit was installed by one of the previous owners. I think, do to HOA rules about things on the outside of the house, they put the unit under the house, which is a royal pain when I want to descale it - just did it, last month. I was also concerned about leaks, under the house, where I wouldn’t normally look, like in the garage or out on a outter wall. So I put in a Moen leak detector. Only trouble is that when it rains really hard, it sets off the detector. The detector is nice, in that it has a thermometer so I can check air temp. I was always concerned about freezing, but I’ve found that our crawl space doesn’t get below freezing if we keep the house at 52 degrees. I do like the units and haven’t had any issue with running out of hot water, The only issue we had with our first one was that it was set to require a certain water draw to kick on, so due to CA low pressure shower heads, the heater wouldn’t turn on and what little water that was in the lines was quickly gone. I think there was some internal switch that we had to set and or we remove the low flow restrainer from the shower head (I don’t think the newer shower head in CA have those anymore). 

That sounds like a worthwhile upgrade, especially if you’ve already had a good experience with a Rinnai tankless system in your previous home. Running out of hot water in the middle of a shower is definitely one of the biggest drawbacks of a traditional tank when several fixtures are being used close together.

Having the plumber verify the gas supply, venting, and expected flow rate before ordering is a smart move. The Home Depot veteran discount is a nice bonus too. I’d just double-check the current federal and local tax-credit requirements before counting on the efficiency deduction, since eligibility rules can change from year to year.

Hope the installation goes smoothly and this ends the cold-shower problem for good.

Update and change

Wife said we MUST keep using the hot water pump, which draws water from the 50 gallon heater and puts it back in the tank after circulating... and can't do that with a Rinnai (or any other on demand unit)

So, no on demand heater

If your tankless unit is very close to your tap, it makes sense.  Otherwise, it doesn't.

Descaling is another issue.  Hard water is no friend to tankless water heaters.

Where we live, a separate ionizer unit is an essential add-on expense.

Good luck with your plumbing consult.  Keep us posted on what you find out.