Insulating Hot Water Pipes

[Topzide]

Here's the unit info that I have mounted under sink.

 

[Popgadget]

I had the same issue- Rinnai combi boiler for radiant heat and hot water. Works awesome, but the wait for hot water at the kitchen sink was unbearable.
It’s the furthest from the water heater, and is in an island on a concrete floor, so the lines go under the slab insulation and radiant heat and surface in the island. They are only subterranean for about 15 feet, but coupled with the overall distance from the water heater, it was unacceptable.

Adding a return line was not really an option, so I got one of these-

https://www.supplyhouse.com/Grundfos-595926-Comfort-Valve?utm_source=google_ad&utm_medium=Shopping_Plumbing&utm_campaign=Shopping_X_Plumbing_X_SSC_New&utm_campaignid=22376725605&utm_adgroupid=175817622854&utm_targetid=pla-2435661369999&utm_product_id=595926&utm_matchtype=&utm_keyword=&utm_adtype=pla&utm_category=Plumbing&gad_source=1&gad_campaignid=22376725605&gbraid=0AAAAAD_WAyt6nqPFqVSoqt8QjzEJgHVKd&gclid=EAIaIQobChMI98ipi93EkAMV-oAiBR1LKyNXEAQYASABEgLnGfD_BwE

There is a flow switch and timer in the boiler which activates the circulator then when it senses the flow from the valve opening it stays on. If the valve is closed the pump only runs for a few seconds. I also have a timer to defeat the system overnight.

 

[IXLR8]

The house I recently purchased had a tankless water heater at one end of the house, it literally took 4 minutes to get hot water to the kitchen sink. It was 130 ft from heater to sink!! I insulated the pipes and it didn't make much difference. I installed a recirculating system, insulated the return line. I used an X-10 system to manually start/stop the recirc pump. Turn the pump on about 1 min before you need the hot water and you are good to go with unlimited hot water. My neighbor put in a recirculating system as he had the same issue with taking forever to get hot water. But he didn't put in any way to control the pump, it runs 24/7, his propane bill is sky high.

 

[rontaki]

I had a tankless WH in one house, with a recirc pump on a timer. I ended up switching the pump to always on, and controlled it with a remote christmas lights switch (radio remote). My complaint with the system was that the TLWH would shut off at the low flow rate I preferred when washing dishes by hand, and other uses. I moved from that house before perfecting a solution to that problem.

My current house came with an electric tank heater. I was planning to install a propane tankless WH, instead installed a solar panel system, so most of the time the sun heats the water, in a roundabout way.

 

[LittleBill21]

insulating pipes doesn't do crap, my entire run is insulated in a constant 60F insulated basement, i can tell you what room it passes through, just based on the water temperature.

get a recirculation pump with a dedicated return, or put a point of use under the sink, nothing else fixes it.

 

[wilso]

I did something similar in my last house and honestly, insulating the hot-water lines made a bigger difference than I expected, especially with a tankless system. Your approach with thicker foam, glued seams, custom 45° cuts, and foil tape is exactly the “do it once, do it right” mindset.

A dedicated return loop is definitely the way to go if you’re already this deep in. The crossover valves work, but that warm-cold mix in the cold line gets annoying fast. The cold-water–sandwich thing does happen with tankless units, but in my experience, it’s a quick blip. Most people get used to it or barely notice.

Also, if you ever redo your bathroom fixtures or plumbing layout down the line, reading bath planet reviews might be helpful. People mention water-use quirks that kind of relate to recirc setups.

 

[HawkinsHollow]

I did something similar in my last house and honestly, insulating the hot-water lines made a bigger difference than I expected, especially with a tankless system. Your approach with thicker foam, glued seams, custom 45° cuts, and foil tape is exactly the “do it once, do it right” mindset.

A dedicated return loop is definitely the way to go if you’re already this deep in. The crossover valves work, but that warm-cold mix in the cold line gets annoying fast. The cold-water–sandwich thing does happen with tankless units, but in my experience, it’s a quick blip. Most people get used to it or barely notice.

Yep! I have already noticed a vast improvement. I still have about 30% left to insulate, but it has made an improvement. I figure the insulation will be super helpful to at least get warm water to wash our hands quickly and save energy when the circulation system goes in. I will even insulate the return line. Warm water getting reintroduced into the line just in front of the heater has to save a bit of energy. Might be able to turn the heater down a bit and get the same performance.

 

[civilian]

We have a recirculating hot water system. Propane water heater. The pump is on a timer that shuts system off at night time. Back on in the morning in time for showers. 3/4" pex outgoing, 1/2" return line. Nothing insulated. All sinks have hot water in a few seconds, even kitchen at end of run with the longest branch to the faucet. Now, at the master shower, hot water takes a few seconds longer to reach it. Recirc loop a bit further away from the branch take off point. Plus shower valve around the corner from where the shower head is. Have thought about preheating the return water by going along the baseboard heat supply line from the outdoor wood boiler. Just haven't replumb it. Jon