Check valve for recirculating hot water

I finally got serious about finding out why the tank water, in the toilet closest to the water heater always ended up hot! I have a hot water recirculating pump with the 1/2 inch output teed into the cold water input to the water heater. Whoever installed this either thought that the returning hot recirculated water would all go into the water heater along with the cold water input -- or didn't care. It has to be that some of the recirculated hot is going back into the cold water system. I looked at some internet info and saw that most systems returned the recirculated water into the drain output of the water heater. My question is: Can I leave things as they are and just add a check valve at the ouput of the cold water input to the heater so that the recirculated hot can not go back into the cold water line? If so what kind of check valve do I need and does it matter if it's mounted horizontally or vertically? The cold water input is 1" diameter.
thanks

I've been using "spring" checks lately, not the check with flapper.
6/7/2014

If you add the check valve at the inlet, use a swing check with a small hole drilled into the flapper.

The small hole prevents "banging", at least it's supposed to.
The check valve needs to be installed so that it is closed when at rest.

The check valve, even with the hole in it will prove to add more resistence than the hot. Thus the pumped water will take the easiest route.

re check valve

Thanks for the response, but I'm not sure what "closed at rest" means. Is "at rest" when your holding it, before installation, in a position where gravity causes the flapper to be closed. That would mean horizontally for the ones I've seen. I apologize if I'm making this more complicated than it is.
thanks again,
stan

hot water

The toilet tank is not getting hot because the pump is tied back to the cold water. It is getting hot because convection is allowing hot water to rise from the tank into the cold water line. A hole in the check valve will allow the action to continue. And if the check valve has to be installed vertically on the cold water inlet, it may have to be a spring loaded one or else it will be upside down. A better solution would be to put a heat trap on the cold water line which is merely a section of pipe that drops down before rising again and connecting to the water heater. I would say it is the same as putting an "S" trap in the cold water inlet, but that might not mean anything to you.

thanks for the input SJ. I do understand S trap and convection and would rather do that then the check valve. However, I turned off the pump for several hours to see what would happen; the toilet tank water no longer got hot (it also took an awfully long time to get hot water on the far side of the house).??

trap

It should as long as the "S" trap is between the main line and the pump's connection. But if you should have to install a check valve, you will also have to install an expansion tank to control the thermal expansion pressure build up.

trap

currently there are no S traps or check valves in the line. What I am really searching for is the best way to solve the problem. The problem is having the hot water flowing back into the cold water inlet to the water heater. I do have a recirculating pump which is connected to the cold water inlet. I don't know whether convection or the hot water returning from the recirculating pump is causing the problem. However I do know that I don't get hot water in the nearest toilet tank (thru cold water system) when I unplug the recirculating pump. I'm looking for the simplest way to solve this problem.
thanks,
stan

pump

The pump can only move the water from its outlet back to its inlet through whatever piping system connects the two points. It cannot circulate water into the cold water pipe, unless there is some way for that water to return into the hot water circulation system. Now, this is not impossible if you have a defective single handle shower valve made by a few particular companies, but that is a different problem and not directly related to the pump issue. Maybe you should check for that before you spend time and money on the pump, because if that is the problem you will still have it and a check valve would just eliminate the symptoms and not cure the problem.

ok hj ; your last input makes the most sense to me! Now I need to know how to test the faucets? I have several single handle moen faucets in showers,baths and laundry room.
stan

Moen makes a great valve but very common to have it allow hot water into the cold system with a recirc. pump.
Best way to test Moen or any valve is to:
1. turn off the hot water and pump.
2 open a separate hot valve in the house
3 You can then put your ear up to any single handle control to listen to water flowing through it. You can definitely hear it.
4 If you do, a new cartridge will fix it
5 on some valves, there are built in check valves to prevent water bypassing within the valve.