Problem with house that had two water heaters and now only has one

[jeffmitchell]

Hey guys. I recently purchased a home that had two side by side water heaters in the basement and now only has one. The current set up is that the hot water outlet has a T and then connects to both main 3/4 lines that supply the entire house. They basically installed a loop to connect both pipes. 4BR 2.5BA home. Family of 4. It is a single 50 gallon gas tank which seems to suffice as we never run out of hot water. The only problem is it seems as some faucets take a really long time to get warm water to them. Specifically the kitchen sink. I need to waste roughly 6 gallons to get warm water. I would like to reduce/eliminate this waste. There are two 3/4 hot water supply lines that run the entire length of the basement next to each other. I am comfortable with working with plumbing and wondering if I should abandon one of the lines and tap in any of the branch lines to one main line?? I don't want to create any flow issues or any other unforeseen problems.

Can someone tell me what some reasons are for a home to have two water heaters and what problems could be caused by switching to only one? Other than my obvious problem. I haven't looked yet but would guess maybe it was to have one servicing each tub. House was built in late 80s.

 

[Phog]

The issue you're having doesn't have anything to do with the change from 2 water heaters to one. It is simply the distance that the hot water must travel is too long. You have to empty all the cold water out of the hot main before you start getting hot out of the tank. You're probably right about the original reason for 2 water heaters. Whatever the reason was, doesn't matter now. The thing you need to do is install a hot water recirculation system with a pump and check valve. Often in retrofit situations it is difficult to install a recirculation return line. In your instance you may be able to simply use one of the two existing hot water lines to do this. (You would need to reconnect anything tapped off the converted hot main over to the other hot main, as the return pipe will now have cool water returning to the heater instead of hot). If you choose to go this route make sure to insulate both the hot line and the recirculation return line wherever possible to decrease heat losses.

 

[Sponsor]

 

[jeffmitchell]

Thank you. I just spent some time researching them and they are pretty neat.

What do you think of this one for cost and simplicity? Looks like it comes with everything needed but no mention of check valve.

https://www.lowes.com/pd/Watts-HRWS-Universal-Steel-Water-Heater-Recirculating-Pump/3135231

I prefer Lowe's to HD for convenience but would love an online recommendation if you have one.

Thank you for the info.

 

[Phog]

There are dozens if not hundreds of different hardware options when it comes to recirculation systems. There are also different ways to do it. It's a topic into itself. Some considerations are (this is not a comprehensive list), how is the recirculated water getting back to the water heater (dedicated return vs. using cold water pipe)? How is the pump getting its electric power? Where is the pump located (underneath sink vs on top of water heater)? How is the system controlled (thermostat vs timer). There is no one right answer. I suggest doing some research and choosing what you feel comfortable with installing.

 

[Reach4]

There are other things to consider. Some, like the one you pointed to have a timer, in addition to a thermostat, to make sure you have instant hot during programmed hours. Some use an occupancy sensor -- stay off until somebody enters the bathroom. The most electricity-efficient have a button to press a little before you want the hot water.

You should insulate your hot pipe, particularly one that runs for long periods.

https://www.energystar.gov/products/water_heaters/demand_hot_water_recirculating_system

 

[WorthFlorida]

6 gallons would take about 2-3 minutes before getting warm water, I'm sure it is less but still a lot of water wasted. One remedy is the 3/4" pipe run to the sinks that are slow to warm up, changing the pipe to 1/2" copper. Coming out of the water heater is usually 3/4" and somewhere things get reduced to 1/2" to the faucets and fixtures. 3/4" copper holds about double the volume of water compared to 1/2" copper.

Many new bath faucets are rated at about 1.5 gallons per minute and some are less and kitchen faucets are 2.2 gallons per minute mandated by law. If they are certified as "water sense" it's 1.2 gallons per minute.

With the second 3/4" pipe that is really not needed with one WH, installing a recirculation system would be easy to install with a basement for access.

https://www.hotwaterproducts.com/service/pipevolumecalculator.html

According to federal regulations, all kitchen and bathroom faucets should have a maximum flow rate of 2.2 gallons per minute (gpm) at 60 psi (pounds per square inch) of pressure; in California and Georgia, maximum flow rates are further restricted to 2.0 gpm (California will eventually be restricted to 1.8 gpm).Dec 18, 2017

 

[Phog]

One remedy is the 3/4" pipe run to the sinks that are slow to warm up, changing the pipe to 1/2" copper.

It's difficult to say one way or the other without seeing the exact layout of the system. Let's say that the farthest downstream fixture is a bathtub & the sinks lines tap off the 3/4" hot main trunk somewhere between the water heater and the tub. Downsizing the trunk to 1/2" could lead to pressure problems if someone attempts to use the kitchen sink while someone else is drawing a bath. (Particularly if the service pressure is low to start with). I agree it's likely that some lines could be downsized but which ones, if any, would be specific to the particulars of the house plumbing.

 

[FullySprinklered]

Lots of good information above.

I install the Watts pump shown in your link. Never had a problem or call-back. You would need an outlet near the W/H. Everything you need is in the box.