Getting a Tankless Water Heater Installed

[Patchules]

"energy savings are not really demonstrable ( any more than replacement windows) and water savings due to waiting for hot water are nil without tandem installation of pex."

What does pex tubing have to do with water savings using recirculation for DHW? Recirc can be used on almost all pipe materials except for any "plastic" not rated for DHW. The recirc line does not even have to be the same material or size. They probably should be within the insulated envelope though as keeping them hot will increase radiant heat loss.

One hotel where I stayed had way too large a recirc pump. It was so noisy all night long. It may have been that way to try to compensate for poor plumbing layout. In one house I built I had a tiny 3/8 in. line from the kids bathroom which was about 70 feet from the water heater and used a small bronze pump on a timer. Ran in the morning and evening only and was silent. All insulated copper pipe.

[Texas_Ranger]

I suspect the idea was that PEX pipes are better insulated and thus don't need a circulation pump for the water to stay hot. To be honest I seriously doubt that, besides there's always foam insulation for other pipe materials. I'd strongly recommend insulationg pipes anyway, including cold water lines. Otherwise you'll get condensation on the cold pipes on hot summer days. I've seen a basement that was flooded (not badly, but there was some standing water) every summer due to condensate on the galvanised cold water lines!

[triguy128]

Dewpoints in the summer in my house are under 60F< even in the basement, so cold pipe condensation isn't an issue.

I got the water heater remote control mounted on the main floor next to the thermostat. Not that I really need to mess with it much, but it satisfies the engineering nerd in me to be able to see if it's running or adjust the temp if desired. We have it set at 112F for now. Seems to be a nice temp for washing hands and you mix in just a very small amount of cold for showers and kids baths.

I raised the temp to 140F and then turned on every hot water tap in the house to try and max it out. NO fault codes, no fuss. Just endless hot water. I don't have enough water pressure however in the house to sustain that many faucets and showers simultaneously it seems. But I can definitely run 2 showers and 1 faucet, DW or washing machine at the same time, no problem.

The plumber is comming back tommorrow to do the recirculation piping.

ON a side note, I drained the 18 y.o tank water heater. Pretty good amount of rusty crud came out at the end and when I flushed it through a few times. I suspect the glass lining is probably compromised since the anode rod dissolved a few years ago. It's a 9 yr tank on it's 13th year. Still look almost new FWIM. It will make a nice emergency back-up.

[Kansas. 1911.]

You're going to keep the old one in place? I loved getting the space in the utility room. Our old water heater was just like the rest of the house--dirty inside and out.

[Texas_Ranger]

Dewpoints in the summer in my house are under 60F< even in the basement, so cold pipe condensation isn't an issue.

What's your incoming water temperature in summer?

[triguy128]

I think in summer the temps are around 60-65F. I think its' already up to the upper 50's with the warm winter we had.

The recirculation system was completed yesterday. It works great! I'm going to call the Navien Rep and get some clarification on some of the operating details. It seems like the circulation pump cycles on and off using some type of logic. It seems to work great. My hot water wait times are about 1 seconds in the kitchen and 5 seconds in the master bath and downstairs 1/2 bath. I have the unit turned to 109F right now. I'm gonna try that for a while. It's cool enough you can wash your hands without mixing cold and almost take a shower without any cold water and still warm enough to hand wash dishes and dissolve grease. The dishwasher has electric temperature boosting, so I don;t need higher temps for that.

So far I can highly recommend the unit... but I might change my mind after I see the final bill form the plumber. I trust him so we just did it time & material. I think the final damage after my utility rebate will be around $2400, but that includes about 5 hours and about 80ft of pipe and 5 new valves for 3 recirulation loops.