Tankless water heater & Recirculation Pump

[Jerry1]

For those who have a tank and a recirculation pump, how do they work? I’ve done some reading and it looks like I’d have to tie into my cold water line to complete the loop. I assume this basically takes away your cold water but we don’t drink from the bathroom sink so that’s probably not an issue. Our only issue is our bathroom. It’s at the other end of the house from the tank water heater. The kitchen and half bath are much closer but if it wasn’t too costly, addressing the kitchen would be nice too. It’s about 1/3 of the house away.

We live in a ranch on a slab with the plumbing running under the slab so there’s no extra plumbing that’s going to happen. The attic is also out of the question. It’s a northern home and the attic is too small (can’t stand up in it) anyway.

Getting hot water quicker to the main bath is the main issue and probably the only issue worth spending money on.

Also, we don’t use a lot of hot water. We have an natural gas 40 gal tank and me and DW can take showers as long as we care to and we’ve never run short of hot water. I think the tank has a short recovery time. I do know that when the flame kicks on, it sounds like a jet engine.

ETA: Only a 40gal tank. Originally thought it was 80.

 

[zinger1457]

For those who have a tank and a recirculation pump, how do they work? I’ve done some reading and it looks like I’d have to tie into my cold water line to complete the loop. I assume this basically takes away your cold water but we don’t drink from the bathroom sink so that’s probably not an issue. Our only issue is our bathroom. It’s at the other end of the house from the tank water heater. The kitchen and half bath are much closer but if it wasn’t too costly, addressing the kitchen would be nice too. It’s about 1/3 of the house away.

I have the Watts recirculation pump installed on my hot water tank and it works very good, no issues with the cold water. Besides the pump there's also a crossover valve you install on the sink furthest from the tank. Fairly easy DIY install.
https://www.watts.com/dfsmedia/0533dbba17714b1ab581ab07a4cbb521/78778-50060/500800-0955800

 

[ERD50]

For those who have a tank and a recirculation pump, how do they work? I’ve done some reading and it looks like I’d have to tie into my cold water line to complete the loop. I assume this basically takes away your cold water but we don’t drink from the bathroom sink so that’s probably not an issue. Our only issue is our bathroom. It’s at the other end of the house from the tank water heater. The kitchen and half bath are much closer but if it wasn’t too costly, addressing the kitchen would be nice too. It’s about 1/3 of the house away.

We live in a ranch on a slab with the plumbing running under the slab so there’s no extra plumbing that’s going to happen. The attic is also out of the question. It’s a northern home and the attic is too small (can’t stand up in it) anyway.

Getting hot water quicker to the main bath is the main issue and probably the only issue worth spending money on.

Also, we don’t use a lot of hot water. We have an natural gas 80 gal tank and me and DW can take showers as long as we care to and we’ve never run short of hot water. I think the tank has a short recovery time. I do know that when the flame kicks on, it sounds like a jet engine.

See zinger1457's reply. Doesn't seem like you'd need any major plumbing changes.

Two considerations I think:

1) You can't get in and insulate pipes in the slab (maybe the hot was insulated before the pour?), so this will suck up some energy, depending how often you are running the circulating pump. They can be set to be on-demand, but to me that somewhat defeats the 'instant hot water' benefit. But if you have a routine, turn it on from the bath, get things ready, then draw hot water... but all you are saving is water, and some energy by recirculating the warming water, you haven't really solved the "waiting for hot water" problem.

And even if the hot is insulated, they probably didn't do the cold, and that now is absorbing the heat going back to the heater, so energy savings won't be so great either.

2) If the plumbing to the kitchen is tapped off the line going to the bathroom, you'll (at least at times) have warm/hot water on the COLD faucet in the kitchen. This may or may not be a concern for you.

edit/add:

Getting hot water quicker to the main bath is the main issue and probably the only issue worth spending money on.

In that case, consider a small water heater close to the bathroom. A small tank (2~5 gallons?) can provide the hot water until the flow gets hot.

https://www.homedepot.com/p/Bosch-4-Gal-Mini-Tank-Electric-Water-Heater-ES-4/206393135

I would think a thermal mixing valve would be a good addition (maybe this is routine, I haven't looked into it). With a mixing valve, you can have the small tank set high temp, and 'stretch' the effective volume of the tank, and keep the temperature constant as the temperature of the main flow picks up, and the tank gets cooler.

-ERD50

 

[zinger1457]

With the Watts I have the timer set for ~12 hours on/off. Here in AZ some type of recirculation system is required in new builds, the purpose is to save water not $$$. Not really sure what the additional cost is to run the system but it seems to be fairly minimal in my situation, well worth the convenience and water savings.

 

[523HRR]

For those who have a tank and a recirculation pump, how do they work?

We have a separate return line to every tap in the house; this avoids returning hot water through the cold water lines. But you can realistically only do this during original build.

 

[Shardo]

Electrician friend of mine said the only way the tankless water heater works is with gas, electricity just can't keep up.

 

[2177V]

I have a tankless at my business and a 40 gal tank at home. They both work fine. If you need lots of hot water then tankless is the way to go. However, the inlet temperature must be high enough for a tankless water heater to work. This will depend of where you are located. If you are in Alaska or Minnesota your hot water may not be hot enough. If you are in California or Florida, you should be OK so you need to check with the manufacturer of the tankless water heater. At my home, the volume of hot water is way less than my business so a conventional water heater is OK.

 

[Deuce]

Tankless water heater’s are twice as expensive and will not last any longer than a standard electric or gas water heater. I would not go for it.

 

[LA_Newsboy]

For those with a recirculation pump, what make is it, and would you recommend it?
I will be shopping for just such a device in the coming months. I'm finally going to get hot water to my wife's bathroom in less than 5 minutes. Thanks for the great thread.

 

[Deuce]

For those with a recirculation pump, what make is it, and would you recommend it?
I will be shopping for just such a device in the coming months. I'm finally going to get hot water to my wife's bathroom in less than 5 minutes. Thanks for the great thread.

I have a thermostatically controlled recirculating pump I’m not sure of the brand but it’s probably $40-$60.

 

[newlyold]

Yes, I have experience with tankless and recirculation. It saves gas, according to the EPA/GOV sites. It requires annual paid maintenance to keep it in shape, and monthly home maintenance by me to keep it running. When there are issues, they are expensive to repair--I spent $1300 a few years after it was installed, as the factory certified plumber tried to get it going again for me. Trip after trip, replaced part after part. Finally the main computer board was replaced and it began working properly again. So much for any savings in propane that year! I like their theory, and we do NOT run out of hot water, no matter how long a shower anyone takes, nor how many loads of laundry are running. But it has ended up be much more expensive to maintain and repair than I expected. I want something that just works, that doesn't need monthly cleaning by me, and that doesn't require an annual visit by the plumber to clean out the carbon / ash build-up that I can't access inside the fire chamber.

 

[FlaGator]

“Monthly cleaning” is a new one for me.

My 5 year old natural gas-fired Rinnai has worked flawlessly in a house of 3+ for five years. Zero maintenance. Not going back to a tank heater

 

[geezee1957]

My 2 cents

We have and have previously had both. Switched one house to on demand. Seemed to save about $15/ month over a typical 40-50 gal gas heater. Sold that one a few years ago. Now have a different place. It had a gas 50 gal. We switched to a Rheem tankless last year. Much the same as far as savings. It is easy to tell because that is the only gas fired appliance we use in the summer. Normal bill for the two of us is 35 a month. I have a crawl space so I installed a recirc pump, and return line. Because I didn’t want to circulate hot water all day, I put the pump on a smart plug. I now say “Alexa start the hot water”. I have it set to run for 3 minutes. Working for us, and doesn’t waste water or gas.

 

[Safe Harbour]

Go to a Hybrid water heater

We have had two Rheem tankless gas water heaters plumbed into a recirc loop for 11 years. It works great, but is very expensive to keep a heated loop warm. I put a timer on the system to turn the recirc loop off from 10.30pm to 6am. That saved quite a lot. The system had a small 10 gallon electric tank water heater to keep hot water for the loop. You don't want to the on demand kicking on every few mins to keep a loop warm, it's very bad for the heater and very inefficient as it has to heat up every time and then loose that heat in cooling down. Electricity for the 10 gallon tank water heater keeping the loop warm was a major electric drain, but better than the having the instant demand gas heaters cycling all the time.

But I finally hit on a better solution. The 10 gallon tank water heater finally rusted out so I had to replace it. I decided to go with a 40 gallon Rheem hybrid water heater. When it's working as a heat pump it uses only about 1/4 the electricity of a traditional (element) tank water heater. It's also highly programable and I have it set to go off at 10.30pm and on at 6am. We so seldomly use hot water during that period, I don't worry about relying on the tankless heaters then and knowing they will take awhile to fill the loop.

The Rheem only cost $1,100 and you get a $300 tax credit for energy efficiency. It is saving about $500 a year in energy costs. So payback is about 2 years and then it's all savings. Not a better energy efficiency investment to be had. It also saves gas because the loop runs longer without support of the instant water heaters. They only kick on when you use a fair bit of water from the tank.

Anyway, I'd put this system up against another arrangement for gas instant water heaters, unless they were all point of use. Also if you just have an normal element tank water heater, it will pay you to replace it now, regardless of age with a hybrid. They are so easy to put in they are basically plug and pay with a traditional tank water heater.

 

[zinger1457]

We have and have previously had both. Switched one house to on demand. Seemed to save about $15/ month over a typical 40-50 gal gas heater. Sold that one a few years ago. Now have a different place. It had a gas 50 gal. We switched to a Rheem tankless last year. Much the same as far as savings. It is easy to tell because that is the only gas fired appliance we use in the summer. Normal bill for the two of us is 35 a month. I have a crawl space so I installed a recirc pump, and return line. Because I didn’t want to circulate hot water all day, I put the pump on a smart plug. I now say “Alexa start the hot water”. I have it set to run for 3 minutes. Working for us, and doesn’t waste water or gas.

You must have some very high gas prices and/or a very inefficient water heater. I have a gas (propane) water heater (40 gal) and during a typical month when I'm not using the furnace (cooking and hot water only) I'm probably using about $10-15/mo of propane.

 

[mpeirce]

For those with a recirculation pump, what make is it, and would you recommend it?.

Some of the TWHs have an integrated pump. Just an option…

 

[tb001]

We have had two Rheem tankless gas water heaters plumbed into a recirc loop for 11 years. It works great, but is very expensive to keep a heated loop warm. I put a timer on the system to turn the recirc loop off from 10.30pm to 6am. That saved quite a lot. The system had a small 10 gallon electric tank water heater to keep hot water for the loop. You don't want to the on demand kicking on every few mins to keep a loop warm, it's very bad for the heater and very inefficient as it has to heat up every time and then loose that heat in cooling down. Electricity for the 10 gallon tank water heater keeping the loop warm was a major electric drain, but better than the having the instant demand gas heaters cycling all the time.

But I finally hit on a better solution. The 10 gallon tank water heater finally rusted out so I had to replace it. I decided to go with a 40 gallon Rheem hybrid water heater. When it's working as a heat pump it uses only about 1/4 the electricity of a traditional (element) tank water heater. It's also highly programable and I have it set to go off at 10.30pm and on at 6am. We so seldomly use hot water during that period, I don't worry about relying on the tankless heaters then and knowing they will take awhile to fill the loop.

The Rheem only cost $1,100 and you get a $300 tax credit for energy efficiency. It is saving about $500 a year in energy costs. So payback is about 2 years and then it's all savings. Not a better energy efficiency investment to be had. It also saves gas because the loop runs longer without support of the instant water heaters. They only kick on when you use a fair bit of water from the tank.

Anyway, I'd put this system up against another arrangement for gas instant water heaters, unless they were all point of use. Also if you just have an normal element tank water heater, it will pay you to replace it now, regardless of age with a hybrid. They are so easy to put in they are basically plug and pay with a traditional tank water heater.

Hmm, that’s interesting. We still have one functioning water heater and I asked them about using it as a reservoir for the recirculation but they said it wasn’t possible. Maybe because the recirculation pump is built in to the TWH?

I have to admit, I’m excited to get all of the space in the closet back. Two large water heaters take up a lot of room! It’s in an outside closet, so all of our gardening equipment, sprinkler repair, etc, will be finding a new home!

 

[Lakedog]

My current house has a tankless (no recirculation pump) mounted on the house exterior near the master bath so hot water takes only a few seconds in the master. For the two baths at the far end of the house, hot water takes just over 2 minutes (timed it after reading some of the replies to this discussion). The kitchen and another bath are closer to the center of the house, and it takes just over one minute for hot water. I can live with these short delays. I live alone and the spare baths are rarely used. The typical single tank water heater does not provide instant hot water to all parts of the house either so not what I see as much of a problem.

 

[ncbill]

Yes, I have experience with tankless and recirculation. It saves gas, according to the EPA/GOV sites. It requires annual paid maintenance to keep it in shape, and monthly home maintenance by me to keep it running. When there are issues, they are expensive to repair--I spent $1300 a few years after it was installed, as the factory certified plumber tried to get it going again for me. Trip after trip, replaced part after part. Finally the main computer board was replaced and it began working properly again. So much for any savings in propane that year! I like their theory, and we do NOT run out of hot water, no matter how long a shower anyone takes, nor how many loads of laundry are running. But it has ended up be much more expensive to maintain and repair than I expected. I want something that just works, that doesn't need monthly cleaning by me, and that doesn't require an annual visit by the plumber to clean out the carbon / ash build-up that I can't access inside the fire chamber.

Yep, is there really sufficient advantage to tankless over connecting a couple of 40 gallon (max capacity) "short" NG tank heaters down in the crawl space like my mom did at her last house?

 

[wildsun]

What is involved in Descaling and how long does it take to do that once a year?

 

[mpeirce]

What is involved in Descaling and how long does it take to do that once a year?

You circulate a mild acidic solution through the unit for maybe 45 minutes. Then flush that out of the system.

There are various valves to fiddle within the units.

Easy, but takes some time. You need a pump and some solution.

Look on YouTube if you want to see how it’s done.