Cast iron valve bodies dominate older water, wastewater, HVAC and fire protection systems. They are strong in compression, cheap to produce and perfectly adequate for low-pressure water service, which is why so many are still in use after fifty years.
The resale market for cast iron is real but price-sensitive. Large gate and check valves in good condition are the strongest items; small utility valves only sell in volume. Flange damage and cracking are the usual reasons for rejection.
Review points
What decides the value of cast iron valves
Flange condition
Chipped or cracked flanges are the most common defect and the most common reason for rejection.
Size
Larger sizes carry the value. Eight inch and above is where the market is.
Ductile versus grey
Ductile iron has a higher pressure rating and a better market than grey iron.
Selling it
How to present the lot
Count by size and pattern, and note the marking on the body. If you have certificates, include them; if you do not, say so rather than implying they exist.
Do not separate trim from bodies to sell them individually unless the trim is clearly identifiable and valuable on its own. In most cases the assembly is worth more together.
Questions sellers ask
Is cast iron worth buying used?
Yes, in larger sizes and good condition. It is not a scrap purchase.
Can cast iron valves be repaired?
Cracks generally cannot. Seat and disc work is possible on some patterns.
Do you buy cast iron butterfly valves?
Yes, in quantity and in good condition.