Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Tankless water heater with storage tank

Looking for a piping diagram for a tankless water heater with storage tank. Most diagrams show street water being fed into the tank as well, which I think is counterproductive. Any insight would be greatly appreciated.
0
Leave a Comment
Categories
- 80.9K THE MAIN WALL
- 2.5K A-C, Heat Pumps & Refrigeration
- 36 Biomass
- 394 Carbon Monoxide Awareness
- 2.6K Controls
- 1.4K Domestic Hot Water
- 3.7K Gas Heating
- 101 Geothermal
- 130 Indoor-Air Quality
- 2.3K Oil Heating
- 30 Pipe Deterioration
- 565 Plumbing
- 4.2K Radiant Heating
- 333 Solar
- 12.1K Strictly Steam
- 36 Water Quality
- 7 Industry Classes
- 52 Job Opportunities
- 7 Recall Announcements
Comments
I don't like to pump off the exact bottom of the tank to the tankless as whatever crap is in the tank then goes to the inlet filter on the tankless and also causes problems. So I pipe to the tankless where Takagi shows their return.
Tankless are designed to make only the set point temp. If the unit is set for 140 it will make only 140. Why return it to the bottom of the tank. That set-up works with a boiler where you get smaller temp gains and a slower rise. I've returned to the hot side of the tank or other penetration on the top or high side. The water is at set point. If there is a draw it is ready to go. If not it will circulate back into the tank and when the A-stat is satisfied you have a tank of HOT WATER. You need a 20* delta T between tankless set point. Lower and the unit may short cycle some. You need a tempering valve on the hot.
Pipe it this way and the tankless is seeing a consistent supply temp and it will smooth right out and gives the best component life.
Check out their Phoenix light duty water heater 76,000 BTU input with 50, 60 or 80 gallon tank high efficiency PVC vented.
Phoenix gas fired water heaters 100,000 - 130,000 - 160,000 - 199,000 BTU input with 55, 80 or 119 gallon tank high efficiency PVC vented
If you go to HTproducts.com look at the Crossover , great price point , firetube HX for DHW and recirc pump is integral .
Langans Plumbing & Heating LLC
732-751-1560
Serving most of New Jersey, Eastern Pa .
Consultation, Design & Installation anywhere
Rich McGrath 732-581-3833
On smaller storage tanks, like 50-gallons, I've had to tinker a bit with maintaining balance between recovery and flow rates at the commercial sinks because no restaurant prep worker wants to know about flow restrictors and aerators. When that happens, I tend to install a master flow restrictor at the tank or tempering valve's outlet so I'm not trying to compete with the flow of multiple wide-open ½"-diameter commercial pot sink faucets. https://www.freshwatersystems.com/p-2019-neo-pure-stainless-steel-flow-restrictor-12-fnpt.aspx
Tanks larger than 50 gallons tend to make me uncomfortable to keep at less than 140°F so I always use a commercial grade tankless heater to maintain a slightly higher temperature on larger storage tanks, or if The Health Department requires a particular restaurant to maintain hotter rinse water at the dishwasher. I'll always find out if the restaurant uses a booster or not.
It gets complicated, doesn't it?
"72°F Mechanical, LLC"
Or email John at [email protected]
John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
For residential service and installations in New Jersey, please see Toro Plumbing & Mechanical and fill out our contacts page, upload pics, and submit, or call (973-672-1000).
Good point on the stratification. Some water heater manufacturers offer special "spare" tube nipples to help with layering of the tank.
It looks similar to the plastic dip tubs you see in tanks. They crimp the end shut then either slot or perforate the tube so the flow spreads evenly across the surface when the nipple is used in a side port.
Easy to build one with copper or pex.
Here is a 3" I built for my solar/ wood boiler storage tank.
trainer for Caleffi NA
Living the hydronic dream
I have a question. HTP shows the Crossover being used as a water heater and in a hydro duct coil heating system without a plate heat exchanger. Does installing it this way pass code?? Don't you want to keep portable water separate form the water used in the duct coil system. I know it cost more to use a heat exchanger but that is the way I would install this type of job.
Langans Plumbing & Heating LLC
732-751-1560
Serving most of New Jersey, Eastern Pa .
Consultation, Design & Installation anywhere
Rich McGrath 732-581-3833
You have to pressurize the tank with line pressure while the pump and burner heat and shuttle the energy.
"72°F Mechanical, LLC"
Or email John at [email protected]
John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
For residential service and installations in New Jersey, please see Toro Plumbing & Mechanical and fill out our contacts page, upload pics, and submit, or call (973-672-1000).
I've been bitten twice by this. Shame on me. Take my word for it. The diagram is solid for 99% of the applications.
"72°F Mechanical, LLC"
Or email John at [email protected]
John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
For residential service and installations in New Jersey, please see Toro Plumbing & Mechanical and fill out our contacts page, upload pics, and submit, or call (973-672-1000).
"72°F Mechanical, LLC"
Or email John at [email protected]
John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
For residential service and installations in New Jersey, please see Toro Plumbing & Mechanical and fill out our contacts page, upload pics, and submit, or call (973-672-1000).
https://us.v-cdn.net/5021738/uploads/editor/ti/iwpqv3bgwacb.jpeg
I suppose to get around the flow restriction of the tankless, you could run the tank and tankless at 160 then use a thermostatic mixing valve.