Two Water Heaters in Parallel: More Hot Water for Busy Central NY Homes

There are two ways to connect two tank water heaters. The difference matters more than most people expect.

• Series: Cold water enters the first tank, and the warm water from that tank feeds the second tank. The second tank does most of the work while the first acts as a preheater.
• Parallel: Cold water splits and feeds both tanks at the same time. Both tanks deliver hot water to the house together, so you get the combined capacity of both units.

For most homes that simply need more hot water at peak times, parallel is the better choice. It spreads the work evenly, it doubles the available flow of hot water, and if one heater needs service the other can keep the house supplied.

Water always takes the path of least resistance. If one heater sits closer to the supply line or has fewer fittings in its path, it will do most of the work while the other barely runs. That tank wears out first and your real capacity is far lower than two full tanks.

The fix is to pipe both heaters so the water travels the same distance and passes through the same number of fittings on the way in and on the way out. Plumbers often call this a reverse return or balanced manifold. In the photo you can see the copper headers running across the top of both tanks with matching connections on each one.

On the job pictured, and on most parallel installs we do, the system includes:

• Balanced copper supply and return headers joined with press fittings for clean, leak free connections.
• A full port isolation ball valve on each heater, so either tank can be shut off, drained or replaced while the other stays in service.
• A pressure gauge on the manifold so system pressure is easy to read at a glance.
• A separate temperature and pressure relief valve on each heater, each with its own discharge line.
• Each tank labeled with the install date and our contact number, so the next person who works on it knows the history.
• Correct wiring or gas supply for each unit, sized to handle both heaters running at the same time.

This home was also on a private well, which you can spot from the submersible pump control box on the wall. We made sure the well system could supply the combined flow before recommending two tanks. You can see this job and others in our project gallery.

An 80 gallon heater or a tankless unit can also solve a hot water shortage. Two tanks in parallel tend to be the better fit when:

• There is not enough height or floor space for a single large tank, but there is room for two standard units.
• The electrical service can support two standard elements more easily than one large specialty unit.
• You want backup hot water so a single failure does not leave the house with none.
• The household uses a lot of hot water in short bursts, like several showers back to back every morning.
• You want to add capacity without replacing a heater that still has years of life left.

Tankless units can be a great choice for some homes, but on wells with hard water or iron they need regular descaling, and very cold incoming winter water in central New York reduces how much flow they can heat at once. We walk through all of these options on our water heaters visits before recommending one.

Two heaters means twice the tanks to look after, but the routine is simple:

1. 1Flush a few gallons from the drain of each tank once a year to remove sediment. Well water in our area tends to leave more sediment than village water.
2. 2Test each relief valve once a year by lifting the lever briefly and making sure it reseats.
3. 3Check the anode rods every few years and replace them when they are heavily worn.
4. 4Keep both thermostats at the same setting so the tanks share the load evenly. Around 120 degrees is a common setting that balances comfort, safety and energy use.

Our full guide on how to maintain your water heater walks through each of these steps. ENERGY STAR also has helpful background on efficient water heaters.

If your family runs out of hot water most mornings, we can look at your current heater, your electrical or gas supply, your well capacity and the space you have, then recommend the simplest fix. Sometimes that is a second tank in parallel. Sometimes it is a single larger unit or a repair to the heater you already have.

Call (607) 373-6421 or request service online. We install and repair water heaters for homes throughout Sherburne, Hamilton, Earlville and the surrounding towns. You can also read more about our water heater installation process.