Hi,
We have had a recirculating line for years and we recently had to purchase a new hot water heater which was the same brand as before. The recirculating line was installed by running a line from the bottom of the hot water heater with a check valve to the furthest hot water line which is the kitchen away from the hot water heater which is in the basement. Our plumber reconnected the recirculating to the new hot water heater and it would not work as well as the old one. I called the Tech Support Line of the hot water heater manufacturer and I told them about the problem and they told me that the newer hot water heaters are not designed to accommodate a recirculating line but they suggested a possibility to make it work by removing the recirculating line with the check valve from the bottom of the hot water heater and install a T in the cold water line that comes into the top of the hot water heater and then to insert the recirculating line with or without a check valve into the T in the cold water line. Our plumber reconfigured it per the Tech Support Line representative but it will not work at all as it is though we never had a recirculating line and it takes forever to get hot water to the kitchen faucet and the laundry room faucet in the next room. The faucets on our main level and other locations get hot water fairly quickly. Does anyone have a suggestion on what may be wrong with the new configuration and what can be done to remedy this problem? Thanks.

Are you using gravity or a pump ?

Gravity

North Carolina Plumber,
I posted that our recirculating line is gravity and the old one worked for years like a charm but when we got the new hot water heater it did not work as well so the manufacturer suggested changing the configuration as I described in my first post. Do you have any recommendations on what the problem is with the new configuration and do you have a suggested remedy short of starting over and installing a recirculating pump? A reply would be most appreciated. Thanks.

pipe it the way it was but remove the heat trap at the hot water outlet nipple.
insulate the recirculation pipe well but leave off about 18 inches at the return end.

A gravity system MUST connect to the drain valve opening. The manufacturer was incorrect saying that heaters are not designed for a recirc connection. Well, they are correct that they do NOT come with a connection, but EVERY heater can be configured with one.

remove the 'heat trap' nipple from the hot - it gives 'frictional resistanc'e to the rise of heat

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

When the "cool" water gets back to the tank it will NOT "rise" to the top of the heater unless there is an infusion of heat to make the water lighter.

hj,

perhaps I used confusing terminology

a gravity circ system works by letting the warmer water 'rise' (less dense), then, as it cools down, 'fall down' and return to the heater and enter the 'bottom'

the heater reheats said water which then attempts to rise again

very very subtle and small 'forces' involved

the heat trap nipple which comes with most heaters today will prevent such 'gravity flow'

ps. the gravity flow loop will only work if the piping is above the heater

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

He stated that the plumber apparently connected the return line to the cold water inlet pipe ABOVE the water heater, and if they followed the manufacturer's advice, may NOT have installed a check valve. EIther one will prevent a gravity system from functioning.

I would like to thank all of those folks who posted comments and suggestions thus far concerning my problem with the configuration of the hot water recirculating line. I appreciate all of you who took the time to respond as your comments and suggestions were most helpful.



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Hospitals, hotels, and other large buildings have used hot water recirculating loops for years. Some of these loops use electrical recirculating pumps while others use gravity. Based upon the fact that your water heater is in the basement of your home, Mother Nature is going to do the work for free!

Gravity hot water loops work because the heated water, which is lighter, rises through the loop. As the water cools at the top of the loop, it falls and is thermo-syphoned back into the hot water heater. The water enters the bottom of the heater at the drain valve inlet. This flow of water is slow but constant.

For a gravity recirculating loop to work properly, the water heater must be located at the bottom of the loop. Ranch houses and two story houses with basements are perfect candidates. Houses built on slabs or that have hot water lines below the water heater must use a simple in-line recirculating pump.

All you need to complete your loop is a return water line from the far end of your hot water line. Locate the end of your existing hot water line. Cut into the pipe at this location. Install a tee fitting. One part of the tee will allow you to reconnect to the hot water line. The other portion of the tee fitting will be the start of the return loop back to the water heater.

Turn off your hot water heater's power supply before you start this project. Then turn off the water leading to the water heater. Drain the hot water heater and remove the drain valve by turning counterclockwise. Install a dielectric union or insulating nipple in place of the valve. This will to reduce corrosion possibilities if you are working with copper or galvanized iron water lines.

To save energy, you must insulate the entire loop. The insulation must start inches above where the hot water line leaves the water heater and must continue along the entire loop as it makes its way through the house and starts its trip back to the water heater. In new construction insulate all of the hot water supply pipe up to each fixture. Do not insulate the last 15 feet of pipe as it gets near the heater. This pipe must be uncovered to drive the convection engine that makes the hot water flow slowly towards this portion of the loop where the water is cooling because of its heat loss through the uninsulated pipe.

The insulation will slow heat transfer but can adversely affect the performance of the loop if you install it over all of the piping. Foam insulation is available which will slide over the pipe as you install it. You can also choose to use premolded fiberglass with a protective coating. The foam insulation is much more user friendly. Remember, to ensure good performance leave insulation off of the last 15 feet of loop piping as it returns to the heater. Be sure this is OK with your local energy code!

If the loop fails to work, water may be flowing backwards through the system from the water heater. You can stop this with a check valve. Install a check valve in the uninsulated part of the loop about 5 feet away from the water heater.

You MUST use a flapper-type check valve, not a spring-loaded one. Spring-loaded check valves will not work and block the slow trickle of water through the loop. Drill a 1/8 inch hole through the flapper so that a small amount of water can flow back to the heater to maintain circulation of the water within the loop. If the loop doesn't seem to work well, slowly increase the diameter of this hole but do not exceed 1/4 inch diameter.

Be sure your heater does not have a heat trap device at the top of the hot water outlet. These are small check valves that stop hot water from drifting up the hot water line when the hot water is not being used. Remove the heat trap device to get the gravity loop to work.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I would like to thank bernabeu (SC) for his recommendations about how to properly install a hot water recirculating line as our plumbers followed your instructions to the letter and the recirculating line now works like a charm. We are so glad we found this website and for all the comments and recommendations were very good but bernabeu (SC) suggestions were very exact and complete and you could tell he knew what he was talking about. Thanks so much for your help.



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Bernabeu, I am having a similar problem as the original poster… Last week I had to install a new water heater and post-install, with the original gravity loop, it takes an incredibly long time to get hot water. I spoke with the plumber and he said that the gravity systems either work or they don’t, and he doesn’t troubleshoot them and goes straight to advising customers to install an electric pump. The fact the gravity system worked so well for so long makes me more inclined to fix it than install an electric pump. I txt’d the plumber your post and did learn he was out of the flapper style return valves and used a spring return valve… could this alone fix the problem? He has offered to swap this valve out. A few things I have noticed that are different from the new installation I have in the basement and your post are the following… (1) the last 15 feet of pipe returning to the water heater have foam insulation and (2) the check valve is only barely 2 feet from the point of entry into the water heater. Another question I had was whether it matters that the pipes exiting and entering the top of the water heater are 3/4 inch and needed an adaptor for the 1 inch house water pipes… the previous water heater was a 75 gallon with 1 inch pipes entering and exiting and the new one is a 50 gallon high recovery heater. Should I be concerned about this? I am new to this forum and would love to know if it is possible to private message or send photos… could I possibly email you a photo of the install. Any thoughts you have are much appreciated. Thanks in advance