Insulating Hot Water Pipes

[HawkinsHollow]

Last winter was a struggle with our new tankless hot water heater. The hot water wait time is agonizing, yes, 100% luxury problems. This is more of a quality of life issue than it is about wasting water or energy. Yes, I hate waste. But I also HATE washing my hands in cold a$$ water all winter. And I am not planning on waiting for 2 minutes to run the faucet for a warm water hand wash.

BUT, there is a solution! And the first step of that solution is to insulate my hot water pipes. Luckily 90% of our new PEX water lines are run through our basement or reasonably accessible crawl space. The rest are in the walls of the house, not much I can do about that. Mind you, I am in SE TN and my basements and crawl spaces do not get below freezing ever. I have decided to go with Armacell Tundra polyethylene foam pipe insulation. It has 1/2 wall thickness as opposed to the HD brand that is 3/8" thickness. Every little bit helps! I am being very careful to do this as well as possible. I am gluing every joint and gluing the slit that allows you to slip it over the pipe. I got 1" insulation to go over the PEX fittings that are bigger than the 3/4" PEX. I am making my own 90s by carefully cutting 2 pieces at 45 deg and gluing them together. And finally I have decided to use the foil tape to cover the outside of the insulation in shiny Al to lower it's emissivity. Again, every little bit helps. HF has 150m rolls of the stuff for $7, no brainer. I am also insulating the 1/2" hot water supply lines that I can reach in the basement. But I am mainly focuing on the main line. With this entire reno/addition project I have tried to do things the right way the first time. I plan on being here for at least 20 more years and I figure the effort will easily pay off over that time period. Here is how it looks.

Any thing I am missing or haven't thought about? This is my first time doing this.

I am leaning towards doing a recirc system. I found one with a timer that has a aquastat on it. The pump runs when the temp falls to 85 deg and turns off when 105 degree water hits the pump. I figure with the pipe insulation it should not run a lot. Also the timer will allow me to shut it off overnight. I was going to use a crossover valve at teh furthest faucet but I now think I am going to do a dedicated return loop. It is only about 20 feet from the last faucet to the hot water heater. The warm cold water that a crossover causes doesn't seem very cool. The only thing I have run into is the issue of cold water sandwiching. Basically the water in the pipes stays reasonably warm but the water in the heater and the heater itself cools off more quickly. SO you get reasonably comfortable water but then get a little "bubble" of cold water from the stuff that comes out of the heater before it heats up enough. Has anyone experienced this? Am I making a bigger deal out of it than it really is? The good thing is I can always add that later if it really is an issue.

 

[Topzide]

I think you're good with the insulation. Adding a recirculation to it would make the tank less heater run more than needed. Recirculation pumps are more for tank heaters with long runs to far off fixtures.

If I had to do all over again, I'd have a gas tank less on the major flow items, showers, washer and kitchen sink. Bathroom sinks I'd put electric point of use tankless units..

Of course I'd insulate all the lines, hot and cold!

 

[steve tym]

I have a recirc line on my hot water. There is a sensor eye in the bathrooms, turns on when it senses motion, turns off when the hot water returns to the pump.
I insulated after the fact. Wish I had when we built the house. I guess I was bored one day. I added 18' of insulation, probably 50' of total line. It made a noticeable difference in the shower.
My brother has an instant water heater at camp. I find it doesn't work well.
If I'm washing the dishes 8' from the water heater, unless I run the hot water non stop, it's never hot.

 

[grsthegreat]

Main reason i hate tankless WH is due to the length of time it takes to get hot water. My water heater is 50’ from master bath. I have recirc hot water system. Pump is only 1/20 hp, so cost is pennies. I know people with tankless that incorporate a small tank WH to use a recirc pump with.

I will never wire up another electric tankless. There next to useless on most residential power panels. Last one i wired took 3 x 50 amp circuits. On a 200 amp panel. All lights dimmed when you open hot water faucet. What a joke

 

[4570Man]

Main reason i hate tankless WH is due to the length of time it takes to get hot water. My water heater is 50’ from master bath. I have recirc hot water system. Pump is only 1/20 hp, so cost is pennies. I know people with tankless that incorporate a small tank WH to use a recirc pump with.

I will never wire up another electric tankless. There next to useless on most residential power panels. Last one i wired took 3 x 50 amp circuits. On a 200 amp panel. All lights dimmed when you open hot water faucet. What a joke

I don’t like them for the cost. The water heater cost almost $2000, my plumber charges an extra $500 to install them vs a regular water heater and we still need a gas hookup that’s like $20 a ft. A basic electric water heater is like $600 and the wire is only like $100. Pretty much every customer is looking for ways to save money and cutting the water heater budget from $3000 to under $1000 and still having hot water is an easy place at start. My only experience with the electric tankless they proved to be incapable of making actually hot water in the winter and I’ve never installed one since. Considering the gas one has a 180,000 btu burner it’s not hard to see why the electric one doesn’t work. I have installed a few tankless gas where the customer was willing to pay and they do make models of tankless ones that are capable of using a recirculating pump.

 

[Topzide]

I have a point of use thankless WH that's on a 20amp double pole. Plenty of hot water for a bathroom sink.

 

[4570Man]

I have a point of use thankless WH that's on a 20amp double pole. Plenty of hot water for a bathroom sink.

Are you sure it’s not a couple gallon tank water heater?

 

[HawkinsHollow]

I think you're good with the insulation. Adding a recirculation to it would make the tank less heater run more than needed. Recirculation pumps are more for tank heaters with long runs to far off fixtures.

Lots of people do recirc pumps on a tankless system. You could be right though with the insulation and using the hot water often enough maybe the water in the line will stay warm enough to enjoy washing our hands. If not a recirc pump will be added.

I have a recirc line on my hot water. There is a sensor eye in the bathrooms, turns on when it senses motion, turns off when the hot water returns to the pump.

I thought about the on-demand with switches and motion sensors. But I like the timer + aquastat option. I don't think it would run all that much with the insulation.

Main reason i hate tankless WH is due to the length of time it takes to get hot water. My water heater is 50’ from master bath. I have recirc hot water system. Pump is only 1/20 hp, so cost is pennies. I know people with tankless that incorporate a small tank WH to use a recirc pump with.

I will never wire up another electric tankless. There next to useless on most residential power panels. Last one i wired took 3 x 50 amp circuits. On a 200 amp panel. All lights dimmed when you open hot water faucet. What a joke

Yeah, this tankless is one of my biggest regrets about things I did during this renovation. They are just not designed for a full sized American household. They are designed for small apartments where there is one wet wall and a few feet of hot water pipes. If I do the recirc pump I have thought about doing a small 4 gallon POU tank water heater as a buffer tank. If not I have heard people complain of cold water sandwiching where the water from the water heater sends a bubble of cold water through the pipes while the heater is getting it up to temp. Hopefully it is not an issue and i don't need it. If so I can add it later.

 

[Topzide]

Are you sure it’s not a couple gallon tank water heater?

Thankless unit. You get a 208 volt AC unit to get good results. Been in use 25 yrs! Chronomite unit. Would work great for a bar sink also.

 

[ponytug]

Lots of people do recirc pumps on a tankless system. You could be right though with the insulation and using the hot water often enough maybe the water in the line will stay warm enough to enjoy washing our hands. If not a recirc pump will be added.



I thought about the on-demand with switches and motion sensors. But I like the timer + aquastat option. I don't think it would run all that much with the insulation.

Yeah, this tankless is one of my biggest regrets about things I did during this renovation. They are just not designed for a full sized American household. They are designed for small apartments where there is one wet wall and a few feet of hot water pipes. If I do the recirc pump I have thought about doing a small 4 gallon POU tank water heater as a buffer tank. If not I have heard people complain of cold water sandwiching where the water from the water heater sends a bubble of cold water through the pipes while the heater is getting it up to temp. Hopefully it is not an issue and i don't need it. If so I can add it later.

I think you are doing great with the pipe insulation. The aluminum foil overwrap might not reduce the heat loss much, but it will slow down any rodents that get in there. As you are considering a recirculating system, I would make sure that the cold water lines get the same treatment.

While I am not a tankless fan due to the water waste, I think that long runs to a faucet are an issue for any water heater. We use a pumped Watts system that bypasses hot to cold at the remote sink(s). It is great, but I would go the pushbutton switch route for a tankless. You want enough flow to get the tankless heating, and then have the pump shut off when the warm water gets to your faucet.

Something like this setup;

What Is Smart Recirculation Control? - On Demand Hot Water Controller

Smart Recirculation Control turns any hot water pump with a dedicated loop and a tank water heater into an on-demand system using a smartphone app controller and a temperature sensing flow meter.

smartrecirculationcontrol.com

All the best, Peter

 

[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