Buy or build?

Which one is right for you?

The honest first question is not "which is cheaper?" but "who will still be maintaining this in ten years?" A ram has two moving parts, and both wear. Whatever you install, someone has to change a valve rubber and re-charge an air chamber. That single fact drives the decision more than price does.

Build it yourself when…

• The site is small — one household, a garden, a livestock trough.
• You are remote, and freight or customs would dominate the cost of a factory unit.
• You want to understand the machine, because that is what keeps it running for twenty years.
• You need it working this month, and you can buy the fittings locally today.

Buy a commercial ram when…

• The duty is beyond DIY scale — large drive flows, high lifts, or both.
• A community depends on it, and you need specified performance rather than a hope.
• You need several units, and want them to behave identically.
• Nobody local will be available to tune a temperamental hand-built machine.
• You need a documented spare-parts channel, so the scheme outlives its installer.

Reading a manufacturer's capacity table

Commercial rams are sold on tabulated performance: delivered flow against drive flow and lift. The tables are usually honest, and almost always quoted for conditions that are not yours. Read them as a family of curves to be adjusted, not as a specification of what you will get.

Find out what the table assumes

• Drive-pipe length and diameter. A ram's performance depends on the drive pipe's length-to-diameter ratio and on how rigid it is. A table generated with a long steel drive pipe overstates what you will get from a short, flexible installation — sometimes by a wide margin.
• Whether "output" means at the ram or at the tank. The delivery pipe and its friction are sometimes excluded from the figures. If your tank is 200 m of pipe away on the flat, that is your loss to add, not theirs.
• Which efficiency is being quoted. The glossary draws the distinction: volumetric efficiency is the fraction of drive flow that reaches the tank, while energy efficiency compares the useful power out with the power in. Volumetric efficiency is the smaller and more useful number for a ram, and it falls as the lift ratio rises.
• The fall used. Performance is quoted per unit fall. If the table assumes more fall than your site has, scale the output down accordingly.

Derate for your site

Take the table's figure for your drive flow and lift ratio, then subtract for the ways your site is worse than the test bench: a drive pipe shorter than ideal, any flexible section, fittings and bends, air entrained at the intake, silt, and a delivery main longer than the test rig's. A cautious 20–30% haircut on a theoretical figure is not pessimism; it is what field experience looks like.

What to check before ordering

• Valve access. Can the waste valve and the delivery check valve be opened and re-seated without special tools? A ram you cannot service is a ram you will replace.
• Spares availability. Ask the price and lead time for a valve rubber, a check-valve disc and a gasket set — before you buy the pump. Order a spare set with the unit. If spares are impossible, walk away, however good the price.
• Wetted materials. Cast iron and brass are traditional and durable; stainless and modern composites appear in newer designs. For potable supply, confirm the wetted materials are suitable (see water quality).
• Pressure rating of the delivery side. It must cover the static head plus the hammer, not just the static head, unless the design guarantees the air chamber cannot fail — see the pressure-vessel case.
• Air-chamber arrangement. Is a snifter fitted as standard? Is the vessel replaceable and pressure-rated? Can its air charge be replenished without dismantling the ram?
• Connections and mounting. Flanged, threaded, or socket? What is the footprint, and does it need a concrete pad? Weight matters for a remote site with no road.
• Noise. Commercial rams can be loud. If it will sit near a house, ask about noise mitigation and mounting.

Then write down what you installed

Whichever route you take, record the model (or the parts list), the drive-pipe length and diameter, the fall and lift as built, and the valve settings that ended up working. That page is what lets the next person re-tune the ram instead of rediscovering it. It is also the first thing a manufacturer will ask for when something goes wrong.

What either option costs over its life is the subject of Costs & community operation. If you are building, start with Build Your Own.