Replacing Check Valve

[SAS]

I have a hot water recirculation system with a return line that connects to the cold water feed of my water heater. There is a check valve on the cold water feed that is leaking. There is also an expansion tank connected to the water heater feed. When I go to change out the check valve, what (if anything) do I have to do to relieve the pressure from the expansion tank? I don't want to cut the pipe and suddenly be drenched by water from that tank. (Or am I misunderstanding how that works?) Can I just open any hot water tap? Open the drain valve on the hot water heater?

 

[Reach4]

Just drain the water. It is not important to release the precharge air.

If the old tank still has water in it (judge by weight and shaking), you need a new thermal expansion tank.

Just to confirm, this is city water, right?

 

[Sponsor]

 

[SAS]

No, it's well water.

 

[Reach4]

No, it's well water.

In that case, I cannot see you needing a thermal expansion tank at all. The pressure tank will serve that purpose along with its primary purpose.

I have to believe that your check valve is not between the WH and the pressure tank. If it is, get rid of it.

And if you have a check valve above ground between a submersible pump and your pressure tank, I suggest you read up on that. Such a check valve would not affect the problem you are addressing, but I thought I would bring it up for your further investigation. It is worth discussing, although it has been discussed.

While we are discussing stuff, this might be a good time to flush your water heater and your pressure tank.

 

[SAS]

The check valve is before the expansion tank, and also before the return from the hot water recirculation line. I need the expansion tank because the check valve will prevent the main pressure tank from being part of the circuit. And I need the check valve to keep the hot water recirculation line from flowing back into the cold water feed.

So, to my original question, can I just open either a hot water faucet or drain some water from the tank to relieve the pressure before cutting out the existing check valve?

 

[Reach4]

The check valve is before the expansion tank, and also before the return from the hot water recirculation line. I need the expansion tank because the check valve will prevent the main pressure tank from being part of the circuit.

Let's be clear. Where do you have check valves? A, B, C, and/or D?
Is your return line teed at the top of the WH (pink line), or does it come in low , as illustrated?

 

[SAS]

I have two check valves at B and D. The return comes into the top of the cold feed to the heater.

 

[Reach4]

I suggest you get rid of the check valve at B. It would be wise to see if anybody disagrees, but I don't see that happening. Once you get rid of the check valve, the thermal expansion tank becomes redundant. You don't need to remove it, but you could.

Sometimes you can take out the insides and leave the housing in place. I don't know if that was the one that is leaking.

 

[SAS]

B is the one that is leaking, and I don't think it can be removed. The diagram shows the hot water heater as the first item in the cold water supply, but it is not. Since there are fixtures before it, removing Check Valve B will allow the hot water recirculation line to pump water into those other fixtures.

 

[Reach4]

That is a reasonable thought. I don't know that that is a problem as long as the tee-point for those cold water loads is not right at the WH. For the pump to pump, it must provide suction, which will draw the same amount of water into the hot pipe. So the flow into the WH will be the same as the flow out.

Many people bring the return line into the drain port, adding a tee for both draining and recirc. It is a 3/4 NPT thread. Some of those systems work without pumps with the cooler water flowing down.

 

[SAS]

Here's what it looks like today. I need to replace that check valve; there's a leak between the valve and the connector below it. As long as I have to take it apart, I figure I'll put in a new valve. The piping looks a bit odd to me - it doesn't seem as if I should need that many bends. Since several of the fittings are so close together, I figure I have to go back to the water heater side of that tee and start from there. Any suggestions on how to best connect all of this together?