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Looking for a solution for Tankless water heater wasting water

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[OP]
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Nov 30, 2016
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Waterloo Region

Looking for a solution for Tankless water heater wasting water

We moved into out home in Cambridge, ON and realized the tankless water system that came with the house is less than ideal. You turn the water on and usually have to wait a minute or two before you get any hot water, and this is worse in winter. Sometimes we need to turn the tap in the sink on as well to get the water hot quickly. And if you turn off the hot water and wait about a minute and try to turn it back on again, you'll just end up with only cold water. This is less than ideal.
I have been looking into switching to a tanked water heater, but space is limited in the house and the only place I can reasonably install the tank would be in the garage.

However I read somewhere that it is possible to install a tank along the hot water line close to the showers and this would theoretically reduce the wait times for hot water.
Does anyone have any experience with this type of booster/reserve tank, or has anyone dealt with a tankless system and solved the prolonged waiting time/water waste?
20 replies
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Mar 13, 2004
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Ontario
From what I have heard you can buy pumps that keep the water flowing so its always warm. Also doing things like insulating your water pipes (if possible) can help them retain heat. There may be other options too I'm not aware of. I would reach out to @newlyborn Hes a highly recommended HVAC company here on RFD that not only installs/Repairs furnaces & AC's but he also does Tankless hot water heaters and regular tank hot water heaters. He may have some good options for you.

Gangsta101 wrote: We moved into out home in Cambridge, ON and realized the tankless water system that came with the house is less than ideal. You turn the water on and usually have to wait a minute or two before you get any hot water, and this is worse in winter. Sometimes we need to turn the tap in the sink on as well to get the water hot quickly. And if you turn off the hot water and wait about a minute and try to turn it back on again, you'll just end up with only cold water. This is less than ideal.
I have been looking into switching to a tanked water heater, but space is limited in the house and the only place I can reasonably install the tank would be in the garage.

However I read somewhere that it is possible to install a tank along the hot water line close to the showers and this would theoretically reduce the wait times for hot water.
Does anyone have any experience with this type of booster/reserve tank, or has anyone dealt with a tankless system and solved the prolonged waiting time/water waste?
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Jan 25, 2007
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Paris
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Feb 8, 2014
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The power up time and the dreaded cold water sandwich. There are solutions such as a small auxiliary tank and running the water at a higher flow rate to get the system running.
I would avoid the recirculator, they eat energy for breakfast, you would be better off getting a full sized tank.
Last edited by Quentin5 on Aug 29th, 2021 12:24 pm, edited 1 time in total.
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Nov 1, 2010
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Kanata
When did you move in? I complained in the beginning as well but you get used to it super quick. Just becomes your daily routine. You're not necessarily "wasting" anything. With a tank you're wasting energy to keep it warm, with other solutions you're wasting energy of some sort.
Uh, yeah, I'd like to speak to a Mr. Tabooger, first name Ollie.
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May 23, 2009
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What is the brand and model of your tankless?

My Rinnai goes into a semi standby state for a few minutes when used in a constant on/off/on/off situation like when hand washing dishes. In this state it’ll ignite quicker (~0.2GPM flo) so it pretty much eliminates the cold water sandwich effect.

For other peak usage times like 6:30-8:30am and early evening I run a recirculating schedule with a Grundfos pump. It recirculates based on temperature in the hot water line or 20mins intervals.
It helps eliminate the long wait time when then tankless has not been in use for a while and shows no changes to my gas or hydro billl.
Sr. Member
Jun 23, 2019
539 posts
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My previous house had a Bosch 199,000BTU tankless that I experienced the same issue with, I would never do tankless again. I would waste so much water waiting for the hot water to eventually come, that any gas savings were offset by the water being wasted. My current house has a 50 gal tank that is more than sufficient for my family. I have yet to run out of hot water while taking a shower, and only need to wait maybe 10-15 seconds before hot water comes out've the tap.
[OP]
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Nov 30, 2016
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Waterloo Region
So glad I got off my lazy ass and asked for help on RFD, you never know what you don't know
sickcars wrote: From what I have heard you can buy pumps that keep the water flowing so its always warm...

Jerico wrote: Ask This Old House provides:
@sickcars / @jerico / @bubuski : This Recirc/Grundfus combo pumps looks like a really solid idea. Low energy, minimum installation footprint/cost and looks like it could be easy to manage and if I understand the idea properly, the cold water isn't being wasted, instead it is pumped back into the cold water line where it gets "recirculated" into the hot water tank. I am going to look into this right away. Thanks for posting.
Quentin5 wrote: The power up time and the dreaded cold water sandwich. There are solutions such as a small auxiliary tank and running the water at a higher flow rate to get the system running.
I would avoid the recirculator, they eat energy for breakfast, you would be better off getting a full sized tank.
If i understand the youtube video correctly, I can run this only when needed. Right now its just myself, my wife and a couple of kids in the house. Hot water use is minimal but super-inconvenient. we only truly need to run this twice a day, and if the pump works as advertised, with start up buttons in both bathrooms, we would not need to run it often. Just hit the button, wait a minute and get into the shower with hot water.
Tabooger wrote: When did you move in? I complained in the beginning as well but you get used to it super quick. Just becomes your daily routine. You're not necessarily "wasting" anything. With a tank you're wasting energy to keep it warm, with other solutions you're wasting energy of some sort.
LOL, you aren't wrong. When we moved in back in March, we spent money looking for a solution and just got frustrated, finally gave up and "got used to it". We worked out the best way to use the hot water and never really complained. However, we had some guests this past weekend, and they could not believe how much water we were "wasting" by letting the tap run for a minute before showers.
bubuski wrote: What is the brand and model of your tankless?

My Rinnai goes into a semi standby state for a few minutes when used in a constant on/off/on/off situation like when hand washing dishes. In this state it’ll ignite quicker (~0.2GPM flo) so it pretty much eliminates the cold water sandwich effect.

For other peak usage times like 6:30-8:30am and early evening I run a recirculating schedule with a Grundfos pump. It recirculates based on temperature in the hot water line or 20mins intervals.
It helps eliminate the long wait time when then tankless has not been in use for a while and shows no changes to my gas or hydro billl.
This is a Bosch unit from Reliance. My long term goal is to replace it with ours, but the thought of how "inefficient" the tankless models were for our house just left us enamored of them.
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Jun 16, 2009
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Woodbridge
You are right that adding a small tank ( electric or gas) may be a good solution to reduce the delay. A circulating pump with a bridge valve can be added too though I personally not big fan of this work around.

Gangsta101 wrote: We moved into out home in Cambridge, ON and realized the tankless water system that came with the house is less than ideal. You turn the water on and usually have to wait a minute or two before you get any hot water, and this is worse in winter. Sometimes we need to turn the tap in the sink on as well to get the water hot quickly. And if you turn off the hot water and wait about a minute and try to turn it back on again, you'll just end up with only cold water. This is less than ideal.
I have been looking into switching to a tanked water heater, but space is limited in the house and the only place I can reasonably install the tank would be in the garage.

However I read somewhere that it is possible to install a tank along the hot water line close to the showers and this would theoretically reduce the wait times for hot water.
Does anyone have any experience with this type of booster/reserve tank, or has anyone dealt with a tankless system and solved the prolonged waiting time/water waste?
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Jun 16, 2009
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Woodbridge
For situations where delay is not bearbale, Rinnai RUR models are the perfect solution. Rinnai tankless RUR199 comes with built in circulating pump / reservoir tank and we install it with the bridge valve. Also RUR models are Wi-Fi equipped. You can just tell Alexa to have water ready before you hit bathroom.
vrscdx wrote: My previous house had a Bosch 199,000BTU tankless that I experienced the same issue with, I would never do tankless again. I would waste so much water waiting for the hot water to eventually come, that any gas savings were offset by the water being wasted. My current house has a 50 gal tank that is more than sufficient for my family. I have yet to run out of hot water while taking a shower, and only need to wait maybe 10-15 seconds before hot water comes out've the tap.
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I could not agree more. I installed my tankless almost a decade ago that was without a circulating pump. Sometimes, I found it annoying initially to wait for 30-40 seconds but overall I have got used to it. Loss is negligible when you compare the energy waste in with water tanks which keeps running intermittently due to heat loss.
Tabooger wrote: When did you move in? I complained in the beginning as well but you get used to it super quick. Just becomes your daily routine. You're not necessarily "wasting" anything. With a tank you're wasting energy to keep it warm, with other solutions you're wasting energy of some sort.
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May 23, 2009
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Mississauga
Check if Bosch has a recirculating pump add-on for your model.

The Grundfos pump I have was sold as a add-on kit by Rinnai. It is an external pump but is wired into the Rinnai tankless unit since my model did not have a built-in internal pump.
I can control the recirculating based on a manual schedule on the pump, the Rinnai app, a button, motion sensor even with Google assistant.

For actual install my return line does not utilize my cold water line as I installed a dedicated hot water return line in my house.
[OP]
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Nov 30, 2016
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Waterloo Region
bubuski wrote: Check if Bosch has a recirculating pump add-on for your model.

The Grundfos pump I have was sold as a add-on kit by Rinnai. It is an external pump but is wired into the Rinnai tankless unit since my model did not have a built-in internal pump.
I can control the recirculating based on a manual schedule on the pump, the Rinnai app, a button, motion sensor even with Google assistant.

For actual install my return line does not utilize my cold water line as I installed a dedicated hot water return line in my house.
Now I am a little confused, the model is a Bosch T9800 SE. It has no wifi module built in but it will accept an external wifi module.
But what's confusing me is that I am not certain if it's got a built in recirculation pump or not. The mini display keeps flashing "recirculation",but it obviously isn't recirculating. What I need to figure out now is whether or not it's got a built in pump. If it has one then I assume all I would need would be a bypass valve upstairs, correct?
If it doesn't have a built-in pump then I would need to install an external system.
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Jun 14, 2008
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newlyborn wrote: I could not agree more. I installed my tankless almost a decade ago that was without a circulating pump. Sometimes, I found it annoying initially to wait for 30-40 seconds but overall I have got used to it. Loss is negligible when you compare the energy waste in with water tanks which keeps running intermittently due to heat loss.
Unless you keep your tank in the shed, the "wasted" heat goes to heat up your house, and without it your heating system has to compensate for it. You are not saving anything in winter, and heat loss is minimum in summer.
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Jan 25, 2007
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Gangsta101 wrote: If i understand the youtube video correctly, I can run this only when needed. Right now its just myself, my wife and a couple of kids in the house. Hot water use is minimal but super-inconvenient. we only truly need to run this twice a day, and if the pump works as advertised, with start up buttons in both bathrooms, we would not need to run it often. Just hit the button, wait a minute and get into the shower with hot water.
The video is an on demand recirculator, there are also whole house constant recirculators that would be on all day. An on demand model should not eat much energy.
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We’re moving into a house that has a tankless water heater so I’ve been thinking about this and have a couple of questions:

1. Waiting 30-40 seconds doesn’t sound like a long wait. In the houses that I’ve lived in (all with tanks) I’ve always had to run the shower for about a minute before getting hot water. So is the delay with a tankless heater much different?

2. From what I understand, with tankless heating you’re screwed if there is a power failure. I can’t imagine that happens enough at the same time people are planning to take showers but is there a way of addressing that scenario? Or not worth it?

Thanks in advance.
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Apr 14, 2009
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Vaughan
newlyborn wrote: For situations where delay is not bearable, Rinnai RUR models are the perfect solution. Rinnai tankless RUR199 comes with built in circulating pump / reservoir tank and we install it with the bridge valve. Also RUR models are Wi-Fi equipped. You can just tell Alexa to have water ready before you hit bathroom.
Ash ( @newlyborn ) put in an RUR unit at my house. I set the app up to turn on the recirc in the morning about 5 minutes before we get up to shower, there is zero delay in the master bath because the hot water is already at the taps. If you want the savings associated with tankless but the quick hot water of a tank, the recirc is definitely the way to go.
Also, it is not just about the shower in the am. I have it integrated with my Alexa, we just tell Alexa to turn on the hot water at anytime and it does its thing. You can have hot water starting to run while you are walking towards the bathroom.
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Nov 9, 2008
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We've had a 199K BTU tankless with built in buffer tank for about 10 years and water is fairly instant to the tap. No recirc line, I'd say within 10 seconds from when we turn the tap on we've got very hot water. We also ran a 3/4" hot and cold copper backbone down the center of the house, and have 3/4" plumbed from the inlet and outlet of the tankless, so I feel that helps. I've definitely waited longer for hot water in homes with tanks.

We went to an Airbnb this summer that had an older single vent Rinnai unit, no idea the BTU and no buffer tank. It tookn FOREVER to get hot water to any of the taps.

Not all tankless are created equal I suppose. I'd also there are other factors, such as the piped distance from the tankless to your outlets, the sizing of your plumbing, the type of plumbing, the way your plumbing has been run etc.
[OP]
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Nov 30, 2016
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Thanks everyone for all of the great input provided here. After searching for on demand pumps available in Canada, in the end i got this pump from Amazon for $199 and installed it myself. Since it's from an unknown Chinese manufacturer, i made sure to add the Asurion 4 year home improvement protection plan for 4 years (only $29.99).
It runs with a barely audible hum and left at it's default setting, it runs every 15 mins or thereabout, but now we get hot water at the shower within 10 secs.
The pump did not come with the remote, but the manufacturer sells one. I do not wish to go that route, so i got a Kasa smart plug and right now it is scheduled to come on for an hour in the morning and another hour in the evening. But I have ordered some wireless (Zigbee) PIR sensors which will be installed in the washrooms/kitchen, which will cause the pump to turn on only when it detects someone in the washroom, or kitchen. Looking forward to see how this works.
[OP]
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Nov 30, 2016
1468 posts
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Waterloo Region
random pattern wrote: We’re moving into a house that has a tankless water heater so I’ve been thinking about this and have a couple of questions:

1. Waiting 30-40 seconds doesn’t sound like a long wait. In the houses that I’ve lived in (all with tanks) I’ve always had to run the shower for about a minute before getting hot water. So is the delay with a tankless heater much different?

2. From what I understand, with tankless heating you’re screwed if there is a power failure. I can’t imagine that happens enough at the same time people are planning to take showers but is there a way of addressing that scenario? Or not worth it?

Thanks in advance.
1. I would add an extra 5 to 10 secs for a tankless water heater in regards to delay. The system has to detect that there is water flowing through before the burner kicks in. I think what really makes ours bad is the distance between the heater location and the showers. Also the hard water causes intermittent blockages to our faucets which reduces the flow rate and was responsible for the low flow rate we were getting upstairs and the consequent cold sandwich or even total failure to get hot water. To remedy this, i installed a water softener over the weekend as well and switched out the shower fixtures and aerators around the house, just to get a new start. So far things are looking great.

2. This is a good question and one i have never given much thought to before. From what I can find online, these heaters require minimal electrical power (just enough to power the sensors and onboard electronics), so I expect a solid backup power solution should be able to provide power in the event of an emergency.

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