Two tankless water heaters?

[lilcuda]

Next year I want to get our house repiped to get rid of the 50 year old galvanized pipes. Our house is a ranch style with the bedrooms and two baths at one end and the garage (where the existing 50 gallon water heater is), kitchen and half bath/laundry room at the other end. We waste a lot of water waiting for it to get hot in the two baths at the far end of the house. I'm thinking of getting two smaller tankless water heaters, one for each end of the house. I also want a water softener installed.

Any thoughts on this plan? Any gotchas other than cost?

 

[STANIMAL]

Not that uncommon , just make sure you have a larger gas line to feed them .

 

[kaymccampbell]

You don't need two water heaters, just a recirculating circuit. It's a third pipe, a taco pump and a little sensor block. It'll put hot water to your faucet without wasting water. There's also one that does it with just two lines, temporarily repurposing the cold water line.

 

[zmaxmotorsports]

You don't need two water heaters, just a recirculating circuit. It's a third pipe, a taco pump and a little sensor block. It'll put hot water to your faucet without wasting water. There's also one that does it with just two lines, temporarily repurposing the cold water line.

 

[lilcuda]

You don't need two water heaters, just a recirculating circuit. It's a third pipe, a taco pump and a little sensor block. It'll put hot water to your faucet without wasting water. There's also one that does it with just two lines, temporarily repurposing the cold water line.

Thought about one of those. It would seem to me that this would waste energy heating the cold water pipes up. Also I want to regain some space in the garage by eliminating the tank water heater.

BTW, what's a taco pump? Does it pump hot sauce?

 

[tomroblee]

If you are replacing all your piping you have a lot of choices. Just to save water a recirculating pump can be a good idea IF your hot water lines are all fed by the same "trunk" line. My rural home is plumbed with PEX using a manifold and separate lines to each fixture in the house. This would require separate recirculating pumps for each "distant" fixture that used hot water.

A recirculating pump can be used with a tank water heat in a manner that the pump runs full time and you will always have hot water quickly available. This will provide convenience at the expense of wasting energy keeping water hot in the pipes. A recirculating pump can be used with a tankless water heater in a manner that the pump runs only when the water heater runs. This will be more energy efficient, but you will still have to wait for the hot water to get to the distant fixtures.

Tankless heaters require a significant quantity of gas or electric. You might have to upgrade your services.

I have a tankless water heater in the garage of my city home. I love it, but it is reasonably loud. This might be a factor if was located in a bedroom area.

 

[58Yeoman]

I have a pump on the water heater with a timer. I set the times of day that I want hot water at the kitchen. IIRC, it pumps hot water through the cold line to the kitchen, where it circulates through a thermostatic valve. When the valve reaches the temp of the hot water, it shuts off the circulation. You will have warm/hot water in your cold water line for a little bit.

I have it set for three times a day for about an hour or so each time. It's worked well for us being on a well. I also had it in my last house which was in town. I think it would be much cheaper/easier than two water heaters.

 

[dirtrich]

We have a tankless (gas) water heater with a recirc. pump.
It works great. You can set the 24 hr. clock on it to recirc. the water every half/whole hr. that you choose.

 

[Showkey]

Recirc system with no pump.....gravity is your friend. But in California with no basement gravity system might be a problem, so pump might be the solution. Two on-demands are not going to be cheap and the maintenance is a royal PIA.

The two on demands goingto be Nat Gas, electric or propane ???

 

[James-W]

This may, or may not, be a good idea, but here goes anyway. What if you had an electric tankless unit under the kitchen sink, or someplace close to that, that just took care of the kitchen hot water. Then you have another electric tankless unit for just the bathroom located in the bathroom, or right next to it. That way the hot water only has to go a few feet to get to the faucet. You can have one in the garage too if you have need of hot water in the garage.

 

[csp]

Taco is a brand, pronounced tay-ko.

 

[silvertop]

Regardless of the type of hot water heater you choose, to be the most cost efficient, it will need to placed as close to the center of the house as possible.

 

[lakeroadster]

When I read the title to this thread, in the spirit of the holidays... I thought:

Two tankless water heaters

.... and a partridge in a pear tree


I think your 2 tankless idea is a good one purely from a convenience standpoint, probably not based on return of investment.

We have a natural gas tankless unit here in our small home (1200 sq ft). It takes the hot water a while to reach the master bedroom, but we've learned to be patient.

 

[Dirtydan69]

I have pex in my house built in 2004. Previous owner installed a pump at water heater, no such thing as a "hot water heater", and loops at all three bathroom sinks. One in the hall bath and one at each faucet on the double bowl vanity in the master. Virtually instant hot water at these sinks. Need to install one on the kitchen. Had a water softener when we bought but couldn't stand the slimy showers and wasn't happy with the RO under the kitchen sink so we installed a whole house filter. Waaaaay better. Great water at every tap in the house.

 

[Showkey]

True on the investment.........I have a conventional NG water heater with a gravity loop and it costs $10-$15 to heat the water per month.

I have condo rental that has an electric on demand heater and it takes five minute to get hot water to the far shower.

 

[TheEquineFencer]

FWIW, if you have teenagers...your gas bill may go out of sight. I was looking at Tankless heaters a while back and talked with a guy at GUC (Greenville Utilities CoOp) about the cost and what was the most energy efficient. I got a real education.

Instantaneous Electric will eat your lunch, conventional with a high Energy rating is a better choice. It cost next to nothing to maintain a hot water tank. Then when it comes on, it just using 3500W -4500W to reheat the makeup water. An instantaneous may be using 12000W or more depending on the heater for about the same length of time. LPG instantaneous is about *** for tat. NG instantaneous is better.

The drawback to the instantaneous is you have an endless supply of hot water. He told me about several customers that has installed them thinking they would save money. Turns out their gas bill doubled and sometimes quadrupled. They went to check out the problem and also found the water usage went up accordingly. The kids were staying in the shower. Before they'd run the electric heater out of hot water and get out, now they were in some cases staying in the shower an hour or longer!

 

[CNGsaves]

^ ^ ^ ^ Endless hot water in shower . . . .
. . AND . .
. . . . . . . . certain occupants
. . .
. . . COULD
. . . . . . . . . . result in HEAVY water useage !!! . .

 

[JRC3]

I have a tankless water heater in the garage of my city home. I love it, but it is reasonably loud. This might be a factor if was located in a bedroom area.

Richmond/Rheem RMTG64DVLN Mid-Efficiency. Maybe HE units are louder?

I've talked to several plumbers over the past 6 months and they were still under the impression that thankless burners run full flame/BTU no matter the volume being used. My guess is those were how older units ran. I've observed mine and it seems to have about 6 levels to the flame depending on volume. The manufacturer advertises down to 11k BTUs at it's lowest draw. This is a mid-end unit and I would expect a better ones to be quieter and have a more adjustable flame and better than .82 efficiency. idk

 

[Tunajoe]

When I built my house, I designed it with 2 on demand heaters.
I installed Noritz brand and 5 years later, no issues at all.
Make sure you put a flushing valve in and follow thru with a water softener. It will extend the life of your fixtures and water heaters.
In previous houses, ive had Bosch, and 2 other brands that I can't remember the names of.
the Noritz have been the best.
With 2 heaters, your gas line has to be up to handling the demand. I have a 1.5" feeding my house.
Also remember, due the cost you will be having them repaired vs installing new. That means you'll be out of hot water till it's repaired. One more reason to have 2 units.

 

[Know Wosad]

^ ^ ^ ^ Endless hot water in shower . . . .
. . AND . .
. . . . . . . . certain occupants
. . .
. . . COULD
. . . . . . . . . . result in HEAVY water useage !!! . .

The simple reality is if a person even knows who BllyZaqueer is. Old Fart Satus
Confirmed.

 

[redmondjp]

I have a Bosch natural gas tankless heater, which replaced a 60-gallon natural gas tank heater (no difference in energy cost whatsoever). My unit is only large enough to run ONE fixture at a time - you don't want to be in the shower when somebody forgets this and uses a sink (you get a cold-water sandwich).

PLUS, the natural-gas-fired tankless heaters, unless they have their own combustion air supply, require a fresh air intake, and they have a large chimney that might as well be a 5" diameter hole in your ceiling. This is not good for energy efficiency!

What I have done, is to install a 2.5 gallon electric tank heater inside my bathroom vanity, which feeds both sinks - INSTANT hot water and just enough for washing hands.

In the kitchen, I have a 4 gallon electric tank heater for the sink and dishwasher (wish I would have used the larger 6.5 gallon unit instead, for hand-washing dishes - 4 gallons is barely enough for the wash water and not enough left for the rinse).

I still use the tankless for the shower and the laundry.

There is more than one way to skin a cat. Having used the tankless for 15 years now, there are benefits and drawbacks. One other drawback of a tankless unit is that you have no on-site emergency water supply, as you do with a tank.

 

[JRC3]

Richmond/Rheem RMTG64DVLN Mid-Efficiency. Maybe HE units are louder?

I've talked to several plumbers over the past 6 months and they were still under the impression that thankless burners run full flame/BTU no matter the volume being used. My guess is those were how older units ran. I've observed mine and it seems to have about 6 levels to the flame depending on volume. The manufacturer advertises down to 11k BTUs at it's lowest draw. This is a mid-end unit and I would expect a better ones to be quieter and have a more adjustable flame and better than .82 efficiency. idk

That vid failed for some reason. Christmas rush I guess.

Maybe my heater is the exception, IDK,

 

[ToddW]

We've had on-demand for 8 years, no problems at all. Our house uses propane for the hot water and cooking, 2 of us we got by on 250G tank for almost 5 years. I have a 2nd I'm installing in the shop. Ours are Rheam units, and there's a sensor that goes out but I just clean it once every 12-15 months and it works fine again. That's about how often I need to clean the burners out from dead critters too coming in the vent!! We also filter the cold water prior to going in the heater due to sediment/well water.

It's about time we flush it I reckon!! Never done it yet. Probably needs it.

 

[lilcuda]

To answer some of the questions, we have natural gas. No teenagers in the house and no plans for any, either!

I'll look into a recirculating pump.

I am curious about what kind of whole house filters people have as we need one of those as well. I assume a whole house filter will take care of the mineral deposits? I have a problem with that as well.

 

[Showkey]

Water test is needed to determine what treatment might be needed:

Dirt sediment= whole house filter

Stinky= carbon filter, some times iron filter, some times other treatments needed.

Hardness, minerals, some iron = water softner

More severe iron issue= iron filter

Acidic water= neutralizer system

Chemical, fertilizers, and other nasty stuff= reverse osmosis system

 

[Voi]

To answer some of the questions, we have natural gas. No teenagers in the house and no plans for any, either!

I'll look into a recirculating pump.

I am curious about what kind of whole house filters people have as we need one of those as well. I assume a whole house filter will take care of the mineral deposits? I have a problem with that as well.

We switched from a NG tank heater to a NG tankless heater many years ago. We are on community well water which is harder than recommended but haven't had any problems.

Our house is about the ideal setup for a tankless heater so I don't have any experience with re-circulating loops, etc.

I have experienced the teenager issue, however, when our niece and nephew were visiting. Took them to the local ski resort for the day and when we got home our niece disappeared into the shower and didn't emerge for a while. We had a talk with her when she got out.

The flip side of the teenager issue is that you always have enough water. One of the last times they were here we had five kids in the house for over a week and we went out and played every day. We couldn't have all three showers running at the same time but there was no issue with anyone waiting for water to heat back up when it was their turn.

Our gas bill went down after the switch but it was part of a major remodel where we made an awful lot of changes so I can't attribute the savings to the tankless heater.

 

[Jackfre]

You can handle this load with a single 199,000 btu tankless 95% water heater. At a 60* delta t you will get high 5's to 6 gpm with that unit. Check your cold water inlet temp. I think it will be 60*. California has some pretty stiff requirements for recirc systems, under Title 24. As they rate recirc systems, no points are given for a time or temperature controlled recirc system control.
I've been running a proto-type system that will be hitting the market in Jan/Feb. It earns max points on T-24. A wireless module is connected to the water heater and communicates with your cell phone. You can register the unit, adjust operation, be alerted by the unit when it needs service and should you choose to do so, you can allow your installing/servicing dealer to see the error codes as well. Control of the recirc system has a circulator installed either in the unit or a separate circ can be added. I have a wireless motion sensor in the bathroom and a wireless push button mounted up under the kitchen cabinet next to the sink. When I walk into the bathroom the pump makes. In the kitchen I push the button to make the pump. I also have an inline sensor in the most remote part of the hot water line. When that sensor sees hot water it will turn the pump off. This system will work best with a dedicated recirc line although it can also work with the Grundfos cross-over tee but you will not have as quick a hot water delivery with the cross-over. As you are re-piping I would strongly recommend the dedicated re-circ line. 3/4" is best. This system will operate any Rinnai tankless from '06 manuf forward. I've reduced my time delay by about 80% and my water waste by as much. Being on a well and as dry as it has been here in the foothills this system is a major plus!