I am installing a hot water recirculation system with a dedicated return line and a circulation pump at the water heater. There are two options for connecting the return line - the bottom of the water heater tank at the drain or to the cold water inlet at the top. I realize that unscrewing the drain hose bib can be a problem if it doesn't come out easily,i.e., it's only plastic and can break. If the connection is to the inlet, then an additional check valve is needed to prevent recirculation line hot water from feeding the cold lines when there is cold water demand in the house. What are the trade-offs?

into the cold side makes a changeout easy.

You do not need an additional check valve because the pump only circulates water through the continuous loop, and the cold water for the house is outside that loop.

If the plastic valve breaks, it can be got out easy enough.

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"You can't get there from here"
Berry/Buck/Mills/Stipe

EATHER WAY WORKS. I PREFER THE DRAIN CONNECTION, BUT PUT THE PUMP WHERE PIPING WORKS BEST FOR YOU.EATHER WAY I WOULD USE A CHECK VALVE BECAUSE IT'S STILL POSSIBLE TO PUSH HOT INTO THE COLD SIDE. IF YOU USE THE CHECK YOU WILL MAKE YOUR HOT A CLOSED SYSTEM.THIS MEANS YOU WILL NEED AN EXPANSION TANK.AN ALTERNATIVE TO THE X TANK IS TO DRILL A SMALL HOLE [ 1/8 ]IN FLAPPER OF THE CHECK VALVE. THE CHECK WILL KEEP THE HOT FROM PUSHING INTO THE COLD , AND THE SMALL HOLE WILL ALLOW THE PRESSURE FROM THE THERMAL EXPANISON TO DISSAPATE INTO THE COLD SIDE .GOOD LUCK

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As far as the recirc goes, I would tie this recirc line back into the cold supply, install a check valve in both the CW and HWR. Make sure you have an expansion tank on the CW side after the check of the cold water supply. I also reccomend ball valves installed on the upstream of the checks.



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I always tie it into the cold water supply at the heater. Personally I think it makes for a cleaner job, and the dip tube sends the water to the bottom of the heater anyways. Instaling a check valve on the circ line does not create a closed system (the heated water can still expand into the cold supply, and consequently into the municipal water supply or well tank), and a check valve on the cold supply isn't necessary as the circ pump is already creating a negative pressure on the hot water.

huh? i have never seen a recirc pump installed without a check valve on the cold line and an expansion tank . at least not by a plumber that knew what they were doing.

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Negative pressure??? You NEED THE CHECK VALVE!

Negative pressure in a loop... A little friction loss I'm sure, but, I'm wondering if I have a gauge that reads that reads that low?

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I think I know what I am doing, and have been doing it for a long time, but have never installed a check valve on the cold supply to the heater, (thus needing an expansion tank), when installing a return/circulator line. And have never had the hot water "back up" into the cold water line, UNLESS it also happened without the circulator line, in which case it is a water heater installation problem, not a circulation pump one.

There has to be a pressure differential across the pump or it will not move the water.

The pressure differential indicated will be the friction loss of the line.

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I've had it happen (hot feeding through cold) more than once. As soon as the check valve was installed no more problems.



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If that were the case, then it would have happened even without the pump system. the pump can only push water into a pipe where the water will cycle back to it, and the cold water line does not fulfil that requirement. And even if it did, the hot water would start at the far, wherever the cross connection was, and work its way back to the pump, meaning that it would still pull through a check valve.



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So we're back to Silicone vs Putty. Out of respect for you, hj(which I hope is mutual). I'm letting this go. You are by far, very knowledgeable and credit to our trade.

WATER WILL ALWAYS FLOW FROM A HIGH PRESSURE AREA TO A LOW PRESSURE AREA IF NOTHING OBSTRUTS IT'S MOVEMENT.THE AMOUNT OF PRESSURE DIFFERENTAL COULD BE MINUSCULE AND THE WATER WOULD STILL FLOW.THE REASONS FOR A DOMESTIC HOT COLD WATER SYSTEM TO HAVE AREAS OF DIFFERENT WATER PRESSURE ARE NUMEROUS. A HOT WATER CIRC PUMP IS JUST ONE OF THEM.

I don't know what the big debate is all about. If you want to do it right, install it at the base. Why? Because the incoming water from the recirc will not mix with the cold supply and it's closer to the control sensor. You don't want to overwork the heater and waste gas. One more thing. Trash the plastic and put in brass. Use a short brass nipple then a brass T for the hose bib and recirc pump connection. Oh yeah, yes you do need a back flow preventer.
Good Luck.

Im with HJ on this one..

There is no way that having the recirc water going back up the cold line is even possible. The pump is pulling the hot side of the tank ( albeit a very long distance) and filling that void in the tank, when the pump shuts off the the checkvalve after the pump but before the T into the cold closes..

Think about it.. Does hot water ever crawl up the cold side of systems that dont have recirc lines?

Thanks to everyone for your comments! I didn't know that the need for the check valve on the cold water inlet (when the return line is connected to the cold water inlet to the water heater) was so controversial. But I wondered about it when a few days ago my plumber said it was absolutely needed along with an expansion tank [or the currently installed Thermal Expansion Relief valve (Wilkens BVEC) on the cold water inlet]. My system has a check valve at the water meter at the street, so city code does require an expansion relief device. I am leaning toward connecting the return at the water heater drain but welcome any other advice.

connect the return at the cold inlet to the water heater, it makes for a cleaner install and future changeout, the dip tube will dispense the return water inches away from the drain outlet had you plumbed it to the drain itself. a check valve on the cold line in absolutely needed, the recirc system will pump into the cold side in periods of high cold usage. an expansion tank must be used and properly located, when the hot side is not being used and the heater hecomes active the volume in this system will expand and will be released out the p&t valve or it may just blow something up.

Because the incoming water from the recirc will not mix with the cold supply and it's closer to the control sensor. You don't want to overwork the heater and waste gas.

If no water is being used there is no "cold supply" the water is just sitting there. When there is water usage, mixing the return water will help preheat it, THERE IS NO OVERWORKING OF THE HEATER AND/OR GAS WASTE.

Oh yeah, yes you do need a back flow preventer

You haven't been listening have you, unless you mean between the pump and the heater?

I'm not trying to be argumentative but I have always tied my recircs back on the cold side and installed a spring loaded check so that if someone chose to open just the cold side of a faucet that it would not cause a cross connection by pulling the water being circed back through. I know that there are heat traps located inside a water heater that are suppose to help reduce back siphonage.I have just always thought that If only the cold side was opened that without a check you have created a cross connection.I might be wrong.

i usually use just a swing check. yes you are correct if installing a circ pump you must have a check on the cold line to prevent a cross.

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I am connecting a recirc line to a side loop water heater and there are no connections other than the cold or the drain port.

I am putting check valves on the return hot before it joins the cold. Also I'm putting a check valve on the cold. I also have a pump on the hot return.

my question is when the pump kicks on and water is sucked out of the top of the heater what will stop the cold check from also sucking open and diluding all that hot water I'm working so hard to recirculate?

The hot water return is definitely backing hot water into the cold water supply in a building I am at. We have 2 hot water tanks, a recirculating pump at the hot water return line near the hot water tanks, and we have warm water when trying to get cold water, everywhere in the building.