Single- or Double-Acting Altitude Valve for Elevated Tank

[OneManWolfpack]

I'm designing a new 0.5 MG elevated tank, which will be filled from an existing distribution system by a 10-inch line. I need an altitude valve to prevent the tank from overflowing. I've seen two different arrangements:

1. A single-acting (one-way flow) altitude valve with a bypass check valve. Flow into the tank goes through the altitude valve. When the tank reaches overflow elevation, the altitude valve closes. As the system pressure drops, water flows out of the tank through the bypass check valve.

2. A double-acting (two-way flow) altitude valve without a bypass check valve. Flow goes into and out of the tank through the altitude valve, which closes when the tank reaches overflow and opens when system pressure drops.

Both arrangements will require an additional bypass line with a gate valve to service the altitude and check valve.

The double-acting altitude valve arrangement allows for fewer valves and a smaller valve vault. I don't really see the advantage of using the single-acting arrangement unless it's a reliability issue. I guess if the single acting altitude valve fails, the system can still get water from the tank via the check valve, whereas if the double-acting valve fails, the tank is shut off completely.

Are there other issues here? Are double-acting valves more problematic? Way more expensive?

Thanks for your help.

 

[bimr]

Yes, there are more issues. How will the pump that is forcing water into the tower be shut off. Or if you have a large system, it may not matter.

Your drawings don't indicate a dedicated 10-Inch fill line. They show a tank being filled by system pressure.

It sounds like you have a zone with lower pressure in which case you would want a pressure reducing valve, not an altitude valve.

Have claval in for a seminar.

http://www.cla-val.com/solution_city.php