2 in or 3 in outlet

What the size means

The size is the nominal bore of the valve: 2 in is DN50 (50 mm), 3 in is DN80 (80 mm). The 3 in bore has a little over twice the area of the 2 in, so with the same head of liquid it passes more than twice as much of a thin product, and the gain is larger with thick ones that drag on the walls of a narrow bore.

When 2 in is right

For water, thin chemicals, solvents and most cleaning products, a 2 in valve drains a tote in a reasonable time by gravity and keeps up with most transfer pumps. It is the common size, so hoses, adapters and spare valves are easy to find. If your other totes are 2 in, staying with 2 in keeps one set of fittings across the fleet.

When 3 in helps

Viscous products. Syrups, honey, resins, heavy oils and gels drain slowly through a 2 in valve, especially in the cold. A 3 in ball valve can cut the time a great deal.

Products with solids. Slurries, pulps and products with fibres or seeds are less likely to bridge or clog in the larger bore.

Fast gravity feed. Where a tote feeds a mixer or a filling line by gravity and the line waits on the tote, the bigger outlet keeps it fed.

Existing 3 in hoses. If your plant runs 3 in camlocks, a 3 in valve saves a reducer on every tote.

Things to check

The valve sits low on the bottle, and a 3 in valve and its handle are bigger. Check there is clearance between the outlet and your containment pallet, drain trough or stand. Not every design offers a 3 in valve, and it costs more than a 2 in. Say "3 in" with the valve type (butterfly or ball) and the outlet connection when you ask, and we'll quote a design that has it. Gasket material applies the same way at either size.

How viscosity changes the answer

Viscosity is a liquid's resistance to flowing. Water is about 1 centipoise; light oils are tens to a few hundred; honey and heavy syrups run into thousands. Through a short valve, the flow of a thin liquid is set mostly by the head of liquid above the outlet, and the size of the outlet matters less than you might think. A thick liquid is different: friction in the outlet and the hose dominates, and a larger bore drains it many times faster.

Temperature changes viscosity too. A syrup that drains well in a warm summer plant may barely move from the same valve in a cold warehouse in January. If your product thickens when cold, size the outlet for the coldest day, or plan to warm the tote with a blanket or a heated room before you draw from it.

Your product's data sheet usually gives a viscosity in centipoise (cP) or mPa·s, which are the same. Send it, and the temperature you draw at, with your request.

Pumps and hoses on the outlet

Whatever the valve size, a pump drawing from a tote should have an inlet no smaller than the outlet, and the suction hose should be short, smooth-bored and free of kinks. A long, narrow suction line starves the pump: it cavitates, rattles, wears its seals and moves less liquid than its rating. For thick products, positive-displacement pumps such as diaphragm, gear or lobe types cope far better than centrifugal ones.

Gravity draining needs the opposite care. Keep the drop from outlet to receiving vessel short, vent the tote's top so air can replace the liquid, and don't let a hose sag into a trap that holds product. Most "slow tote" complaints turn out to be a closed vent, a crushed hose, or a strainer basket choked with skin from the last batch.

Short answers

What size is a standard tote valve?

2 in, or DN50.

Does a 3 in valve drain twice as fast?

The bore has a little over twice the area, so with thin liquids it passes roughly twice as much; with viscous products the gain is often larger.

Can I put a 2 in hose on a 3 in valve?

With a reducer, yes. It gives up most of the larger valve’s advantage.

Can I put a 2 in hose on a 3 in valve?

Yes, with a reducer, but the flow is then limited by the 2 in hose. The larger valve helps most when the hose or pump inlet is large too.

Why does my tote glug when it drains?

Air is fighting its way back in through the outlet because the top is sealed. Loosen the cap or open the vent, and the flow becomes smooth and quicker.