On/Off valve in diverter line

[CygnusSailor]

If the Y valve on the cold water side directs cold water into the water heater OR into the diverter line, what is the purpose of the On/Off valve in the diverter line? Couldn't the diverter line just be a line between the hot and cold water sides without the On/Off valve?

[Hamops]

You ask an interesting question and this should you supply you with the answer. If you were to look at the valve spool of the diverter valve it'll have three ports. When the valve is set to "Summer", it is directing water to both the water heater and the bypass valve. The bypass valve is closed so the cold water doesn't get into the hot water lines. When the divertor valve is switched to "Winter" the cold water is directed only to the bypass valve and bypass is open to run water in the hot water system. These two diagrams should make things clear.

[NH Horseman]

In winter mode, what stops cold water from going into the water heater from the outlet side? Is there a one-way valve in that line?

[CygnusSailor]

OK, I accept your answer that the diverter valve directs water both ways when it is in the summer position. I thought that it was directing the water either to the heater OR the bypass, but never both. This begs the question...What is the advantage of using a valve that directs the water to the heater and the bypass at the same time? Why not use a diverter valve that only does one or the other?

Thanks,

[CygnusSailor]

As I understand it, there is a one way valve, called a "check valve," on the output side of the water heater.

[dalemac377]

That is correct. There is a one-way check valve on the hot water outlet of the water heater.

[Hamops]

Originally Posted by CygnusSailor

OK, I accept your answer that the diverter valve directs water both ways when it is in the summer position. I thought that it was directing the water either to the heater OR the bypass, but never both. This begs the question...What is the advantage of using a valve that directs the water to the heater and the bypass at the same time? Why not use a diverter valve that only does one or the other?

Thanks,

The simple answer is that 2 valves are cheaper than 3. 3valves are required to perform the same function that the 2 valves do. It's likely that the cost of the two valves and check valve is less than the 3 valves.

[avvidclif]

That makes no sense. A "T" valve inputs in the middle and outputs to either of the other 2 ports, not both just one, heater or bypass. No other valve needed, just a check valve.



I have often wondered about that and your drawing makes sense the way is drawn but why use a 3 way valve or whatever you call it????

[avvidclif]

Excuse me, according to Wikipedia the valve you have drawn is a "T" valve. The one I'm thinking of is a "L" valve.

[Hamops]

If you substitute an L valve for a T valve you'll see that the system will only work in the Winter mode. That is why a T valve is used.

[avvidclif]

Swap the bypass and supply lines.

[Hamops]

Originally Posted by avvidclif

Swap the bypass and supply lines.

YEP, that works!