Tankless hot water heater... school me.

[DaytonaBabe]

Time to tap into the vast wealth of knowledge here on RDP...

Our new house came with a tankless water heater. I love having unlimited hot water. The issue, however, is the time that it takes to get hot water from one side of the house to the other (3,100 sq ft, single story). It takes 1:36 to get hot water to our master shower and that's one of the closest taps [emoji44] I'm certainly no Greta Thunberg, but damn, it just isn't right how much water we are wasting every day. With the water issues these days it bums me out to be wasting so much.

I've heard that there is a recirculating pump or something that can help speed the hot water to the tap, or keeps hot water in the lines? School me. What am I looking to buy?

 

[hawgty55]

Just rock it they're great. But yes a recirculating pump would give you hot water faster

 

[DarkHorseRacing]

You'd be in the same situation with a regular water heater as well. While both will make your water hot, you still have to flow that hot water to the taps you are using.

If your hot water heater (tankless or tank) is so far away that running the hot until it gets hot is a concern, then you need to move the hot water source closer to those taps.

You could put another tankless heater into the plumbing just prior to the master bathroom if that's where you feel the issue is the most severe.

ETA: Tankless heaters can be overwhelmed by other devices using hot water (so one of the sizings is flow rate). Are you running any other hot water uses at the same time as the shower? Also, sometimes it takes a bit for the tankless heater to get the water hot because the water has to pass through the entire heater element to get warm to the correct temp. You could see what the temp is the tankless is set for and maybe increase it. Probably should be set for 110-115F. Assuming your cold water is 60F that winds up being a 50F increase in water temp.

 

[NicPaus]

Since you probably don't have a dedicated return line. Have to use one of these.

 

[PlumLoco]

Recirc pump is cheaper and easier for sure. We ran into the problem of getting scalding water from the cold tap in the summer because of how hot the attic would get. Most of the copper is insulated but not all up there. Circulating it helped keep things at least cooler, but never cold in the summer. And this house is in Corona, not at the river. ☹

 

[Activated]

Watts Hot Water Recirculating System with Built-In Timer 0955800 - The Home Depot

Never wait for hot water again; The Watts Hot Water Recirculating Pump provides hot water at every faucet or shower when needed, eliminating wasted water. It is easy to install on any water system and

www.homedepot.com

 

[Done-it-again]

They suck. Having one for 8yrs now and no savings in gas and takes forever for hot water. If wanting a recirc you needed to be plumped for it In the beginning. I wasn’t.

Don’t forget, you need to clean the system out 2x a year.

next would be a lager take unit with a recirc systems

 

[Bigbore500r]

You need a recirculation pump ("recirc" pump).

The right way to add it, is to have dedicated return line from the farthest fixture from the water heater. You can add one that just helps push the the water thru the existing"send" but that won't be as effective.

You can run them on a timer so they aren't sucking power all night while your asleep, and that also helps save on the gas usage a bit too since it's not heating water and sending it.

 

[LargeOrangeFont]

You'd be in the same situation with a regular water heater as well. While both will make your water hot, you still have to flow that hot water to the taps you are using.

If your hot water heater (tankless or tank) is so far away that running the hot until it gets hot is a concern, then you need to move the hot water source closer to those taps.

You could put another tankless heater into the plumbing just prior to the master bathroom if that's where you feel the issue is the most severe.

This. Yore house is too big

 

[thedan]

Watts Hot Water Recirculating System with Built-In Timer 0955800 - The Home Depot

Never wait for hot water again; The Watts Hot Water Recirculating Pump provides hot water at every faucet or shower when needed, eliminating wasted water. It is easy to install on any water system and

www.homedepot.com

^^^^I use this plugged into a smart plug. Comes on 10 minutes before the morning alarm. It is awesome. I can manually turn it on from the app or in the garage. App has a timer to shut off after x minutes too.

 

[Universal Elements]

They suck. Having one for 8yrs now and no savings in gas and takes forever for hot water. If wanting a recirc you needed to be plumped for it In the beginning. I wasn’t.

Don’t forget, you need to clean the system out 2x a year.

next would be a lager take unit with a recirc systems

I use one of these, helps a lot

Smart Descaler - Solve Hard Water Issues | HQ Hometek

Hard water and contaminants are a risk to your family and your home. Find out about our Smart Descaler, the eco-friendly limescale remover.

www.hqhometek.com

 

[SoCalDave]

Unfortunately that Watts system can't be used with a tank-less water heater.

 

[SoCalDave]

I use one of these, helps a lot

Smart Descaler - Solve Hard Water Issues | HQ Hometek

Hard water and contaminants are a risk to your family and your home. Find out about our Smart Descaler, the eco-friendly limescale remover.

www.hqhometek.com

Snake oil...

 

[Universal Elements]

Snake oil...

Yeah ok, sounds good

 

[monkeyswrench]

I have a recirc pump, set on a timer. For us it is to save propane and water. I have seen some fixtures that bleed the "hot" water into the cold side until warm...but more of an east coast/frozen tundra thing.

 

[Spudsbud]

DB, and others......
Cost aside. Speaking in Physics here.
If piped correctly, you do not need, and frankly, do not want a recirc pump. 1 more mechanical device maintain.
You do need a 3rd pipe. Usually 1/2" copper. At your bathroom end tied into the highest point (very important) on the HW side before the bathroom.
At the water heater end tie into the lowest. On Water heater tanks. We would unscrew the drain spigot off the bottom, put a nipple and a tee (standard 3/4" NPT) in and then the drain spigot back in. tie in the return line to the Tee.
Point being, HW rises. Pushing thru the pipe thru convection, pushing cooler water back down the return to the bottom of the tank. Heat migrates up. No pump necessary if it set up correctly. Same principle that keep hot air ballon aloft.
Ask any old plumber. Should work on tankless but Idk for sure.
FYI, Pipefitter, 42 yrs. Retired.

 

[KMH]

Don't worry it wont be a problem when it's 115Deg

 

[rivermobster]

I have a hot water recirc system on my house. We have a raised foundation, so it was easy to plumb. I also have a 70gallon water heater sitting outside the house.

Wouldn't a recirc system with a tankless heater use a MASSIVE amount of gas? Seems to me that the heater would be running non stop in the winter!

Wouldn't you be trading a wasting of water, for gas??

 

[hallett21]

DB, and others......
Cost aside. Speaking in Physics here.
If piped correctly, you do not need, and frankly, do not want a recirc pump. 1 more mechanical device maintain.
You do need a 3rd pipe. Usually 1/2" copper. At your bathroom end tied into the highest point (very important) on the HW side before the bathroom.
At the water heater end tie into the lowest. On Water heater tanks. We would unscrew the drain spigot off the bottom, put a nipple and a tee (standard 3/4" NPT) in and then the drain spigot back in. tie in the return line to the Tee.
Point being, HW rises. Pushing thru the pipe thru convection, pushing cooler water back down the return to the bottom of the tank. Heat migrates up. No pump necessary if it set up correctly. Same principle that keep hot air ballon aloft.
Ask any old plumber. Should work on tankless but Idk for sure.
FYI, Pipefitter, 42 yrs. Retired.

Trying to think how that would work on a tankless. There’s no “reservoir” for the water to push back to.

The tankless heater only turns on when water flow is present. Unless maybe I’m not picturing it correctly.

Either way cool setup on a tank unit for sure.


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[Echo Lodge]

Wouldn't a recirculation pump on a tankless require the tankless to run all the time (or as long as the pump is on)? Seems like it would put a lot of extra mileage on a tankless.

 

[Singleton]

recric pump.
when we remodeled the master bath, we looked into tankless.
with the run required we were told we would need 2. One in garage to service kitchen and downstairs bath and thr. 1 upstairs for all the bedroom bathrooms if we wanted hot water without the long wait. Ran the numbers and said F it, not worth it.

 

[2Driver]

Doesnt a recirc pump defeat the purpose of tankless because its off until you need hot water. Wouldn't a recirc make it be on all the time? We had one on our old house and it just made the water heater cycle on more as the lines become a big radiator

We have the same deal Mel, master is 100’ away. I just turn on the tub as it isnt restricted and water gets hot fast. I still waste the same, but fuck it, if the local golf courses can use 80 million gallons a day I can drain a few gallons.

 

[HOOTER SLED-]

Suck it up buttercup....and get in that shower cold at the start...don't start getting all princess on us.

 

[JBS]

The tankless is not the problem the fixtures are. I had the same issue. It takes so long to get hot water as you are not flowing enough water to purge the pipes.

The first thing you can try is adjusting the mixing valve in the shower to allow more hot flow. When that is not enough remove the flow restrictions in the shower heads. This will solve the issue.

Before I did this I would turn on both sinks with water saving restrictors and the shower. Now I flip the shower on and have hot water everywhere in a short time.

 

[Outdrive1]

Just take cold showers. Problem solved. [emoji106]


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[Outdrive1]

Totally kidding. Cold water is a luxury in the Keys. The pipes go over the bridges and in the summer, you literally have zero cold water. I hate filling my dog bowls with hot water. [emoji1418]


On you tankless heater, why not install one on the other side of the house? So you have two?


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[squeezer]

Have a love hate relationship with tankless systems. In the right house with the right people they are great. The reality is that combination is pretty rare.

Have installed then removed two of them over the years for differing reasons...

The PDF linked in this article is pretty good at explaining some fixes for your problem.

Why Add a Tank to a Tankless Water Heater? - Fine Homebuilding

Ever been hit by a sudden blast of cold water in the middle of your hot shower, or even just lost hot-water pressure altogether, because someone has decided to do the dishes at the same time you're cleaning up? If so, your house might be a candidate for a tankless, or demand, water heater...

www.finehomebuilding.com

 

[Mandelon]

Toss a five gallon bucket in the shower and see how long it takes to fill up.

It may not be as much as you think. The new low flow shower heads only flow 2 or 2.5 gallons a minute. It may seem like an eternity when you are
standing there naked waiting to get in, but it may not actually be that much water.

Oh, then use the water in the bucket for watering your house plants. I suggest you do that naked too.

 

[steamin rice]

I don't have any experience on tankless water heaters, but I have a recirc pump at my house and it's great. Hot water right away at all of the faucets is really nice, and I'd highly recommend adding this if it's an option with you system. Like others have already brought up, it seems like the tankless system would be running all of the time with a recirc pump so maybe it's not a good option with your system. Perhaps a smaller tankless system can be installed in the master bedroom?

 

[NicPaus]

The Grundfos i posted has a thermostat. Once it hits temp its stops circulation. So the tankless would only fire up when pump is on. It will warm up the cold line some as it forces the water back through cold line. Ideally you plumb it from get go with return line but in this case unless you add a return line it is your cheapest solution.

 

[Echo Lodge]

The Grundfos i posted has a thermostat. Once it hits temp its stops circulation. So the tankless would only fire up when pump is on. It will warm up the cold line some as it forces the water back through cold line. Ideally you plumb it from get go with return line but in this case unless you add a return line it is your cheapest solution.

So its heating all the hot water run pipes in your house all the time? Unless they are all insulated it seems like it would run a lot.

 

[Mandelon]

It should have sensor. I believe it works by running the hot water into the cold side under your sink. It would pump hot water into the cold side until it senses there is hot water at the fixture. It then shuts off. You would put it on a timer or a switch so you could turn it on. In a minute or two the hot water reaches the faucet and it turns itself off automatically. No water wasted, just some extra gas at the heater. You activate it, then brush your teeth. By the time you're done, you have hot water at the ready.

 

[SBMech]

I'm not a plumber, but I do live in an area that is pretty affluent and have talked to, been in many homes with tankless hot water.

The only ones worth a damn are the systems installed with radiant heating in the floors (giant recirc system) or the builders smart enough to use mini tankless on every room.

1 per each shower/hot water outlet. They are smaller, less prone to issues, and work instantly, like advertised. Taking a 20 minute hot shower in a modern bathroom with multiple heads....heaven!

 

[NicPaus]

So its heating all the hot water run pipes in your house all the time? Unless they are all insulated it seems like it would run a lot.

Most run a timer. My GF house no timer with 5 bathrooms her recirculating pump runs a lot. I hear it all the time kicking on when in the garage. But it has a return line and hot is almost instant throughout. Very nice compared to my house where I have to wait 30 seconds. All new houses or remodels require 1" insulation on the hot pipes now. This is left over from house I am working on.

 

[DaytonaBabe]

Thanks everyone for all of the input! Except Hoots [emoji6][emoji38] - I'm a cold water sissy.

Many great points made and expertise shared. Lots to consider here. We definitely won't be installing a second tankless anywhere - doesn't go with the decor, ya know. [emoji38] Jeff made a great point and I'll have to take a look at adjusting the crappy hippie flow restrictors to see if that helps. The master takes awhile to warm up, but I can find things to do while I wait to get in the shower - lol [emoji6] The kitchen is the furthest from the water heater and is definitely the most frustrating to not have immediate hot water. Maybe I'll have to see if there is some contraption that can be put under the sink to address that issue. This will all probably be much less of an issue in the summer when things heat up.


No (live) indoor plants to speak of,@Mandelon , so I guess I'll have to take the excess water to the front yard landscaping. Naked, of course. [emoji38][emoji38] Should be a great way to meet the neighbors! Lol


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[Echo Lodge]

I have had the same Takagi for 18 years. It's in a small 1300 sqft home in Huntington. The first thing I did was remove all the flow restrictors in the showers. I am diligent about descaling it every six months. I have to clean the ignitor every once in a while. This thread reminded me to clean the ignitor which I did today. House is so small I get hot water pretty quick at all faucets. I originally got it as the three girls in my house would kill the 40 gal water tank on a regular bases. Also liked gaining the room in my garage when I put up the tankless. Great info on tankless in the thread!

 

[Gonefishin5555]

I have an old school water heater for the downstairs and a tankless for the upstairs. The tankless is mounted to the exterior wall of the house and pipes hot water up to the second floor it takes about 30 seconds to get hot. The old school heater is in the garage and closest to the kitchen and w/d. My first tankless lasted 8 years and my second one cost about $1700 with installation, Im not sure its worth it.

 

[530RL]

Don’t you need a return line when the house was built to run a recirc pump?

We have them at our house but disconnected them as there is a history of copper pipes getting small holes due to recirc?

I suspect her new house has pex and not copper?

 

[Bobby V]

Thanks everyone for all of the input! Except Hoots [emoji6][emoji38] - I'm a cold water sissy.

Many great points made and expertise shared. Lots to consider here. We definitely won't be installing a second tankless anywhere - doesn't go with the decor, ya know. [emoji38] Jeff made a great point and I'll have to take a look at adjusting the crappy hippie flow restrictors to see if that helps. The master takes awhile to warm up, but I can find things to do while I wait to get in the shower - lol [emoji6] The kitchen is the furthest from the water heater and is definitely the most frustrating to not have immediate hot water. Maybe I'll have to see if there is some contraption that can be put under the sink to address that issue. This will all probably be much less of an issue in the summer when things heat up.


No (live) indoor plants to speak of,@Mandelon , so I guess I'll have to take the excess water to the front yard landscaping. Naked, of course. [emoji38][emoji38] Should be a great way to meet the neighbors! Lol


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I see a lot of under the sink water heaters in the office buildings we work in due to lack of water heaters close bye. Most are for the lunch areas for the office and bathrooms in a warehouse. Not sure how they work in your case

 

[Bobby V]

Just checked some job site photos. This is what I was referring to. @DaytonaBabe

 

[DaytonaBabe]

Don’t you need a return line when the house was built to run a recirc pump?

We have them at our house but disconnected them as there is a history of copper pipes getting small holes due to recirc?

I suspect her new house has pex and not copper?

Yep. You're correct. It's pex, not copper.

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[DaytonaBabe]

Just checked some job site photos. This is what I was referring to. @DaytonaBabe
View attachment 971315

Thank you! I'm gonna do a bit of digging to see if that might be a solution for the kitchen [emoji106]

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[JDub24]

Having done high end residential and big commercial jobs for the last 20 years I always asked my lead plumber what they had at their house. Not one of them had a tankless if that tells you anything.

That being said a recirculating system will help but will not be perfect. Also tankless require a lot more maintenance if you want them to live a long-ish life. Water filtration/ RO system is your friend.

Time to tap into the vast wealth of knowledge here on RDP...

Our new house came with a tankless water heater. I love having unlimited hot water. The issue, however, is the time that it takes to get hot water from one side of the house to the other (3,100 sq ft, single story). It takes 1:36 to get hot water to our master shower and that's one of the closest taps [emoji44] I'm certainly no Greta Thunberg, but damn, it just isn't right how much water we are wasting every day. With the water issues these days it bums me out to be wasting so much.

I've heard that there is a recirculating pump or something that can help speed the hot water to the tap, or keeps hot water in the lines? School me. What am I looking to buy?

 

[SoCalDave]

I see a lot of under the sink water heaters in the office buildings we work in due to lack of water heaters close bye. Most are for the lunch areas for the office and bathrooms in a warehouse. Not sure how they work in your case

^^^This for your kitchen. Buy a 1.5 or 2.5 gl electric water heater and mount it under your sink. Plum the hot water into it as a feed. Instant hot water and once the tankless starts flowing hot water into it it will shut off and feed off the tankless.
I have a A.O.Smith (2.5gl) one for my outdoor kitchen for 5 years and it has been flawless.

 

[Justfishing]

Tankless are not instant. The water is cold and the heater is cold. It takes time for the gas to fire and heat the water. This adds to the time it takes to get water to the other side of the house.

A small electric heater close to the master bathroom will provide hot water quicker. The on demand then provides the tank with hot water. The tank becomes a pass through.

 

[Turnup]

I'd say there's something wrong with the tankless, 1:36 to get hot to shower??!! Dang. I like the idea of doing the smallest electric w/h dedicated to that shower/bath or other area too but then damn why have a tankless, put a nice tank unit in worst case scenario. Recirc would be a no go.

 

[DaytonaBabe]

I'd say there's something wrong with the tankless, 1:36 to get hot to shower??!! Dang. I like the idea of doing the smallest electric w/h dedicated to that shower/bath or other area too but then damn why have a tankless, put a nice tank unit in worst case scenario. Recirc would be a no go.

There's nothing wrong with the tankless itself, the hot water just has a long way to travel.

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[DaytonaBabe]

^^^This for your kitchen. Buy a 1.5 or 2.5 gl electric water heater and mount it under your sink. Plum the hot water into it as a feed. Instant hot water and once the tankless starts flowing hot water into it it will shut off and feed off the tankless.
I have a A.O.Smith (2.5gl) one for my outdoor kitchen for 5 years and it has been flawless.

View attachment 971330

I'm thinking this might be a perfect solution for the kitchen. Thank you!

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[NicPaus]

SoCalDave is spot on if you don't use a recirc. Eemax makes a nice small 110 unit that will fit in the sink base cabinet. I bought 1 for $205 when covid hit for the job site so guys could wash there hands with hot water and soap.

 

[Instigator]

Too late now but you could have plumbed the house doing home run plumbing with seperate hot and cold manifolds next to the water heater or heaters if the house is too big. We did that in the last house we built. Longest hot water line held about 1 gallon of water that needed to be purged before you got hot water direct from the heater.
Costs a little bit more to build but no connects anywhere except the manifold and the fixture.
I will do the same thing again on the next build.