Myths & misconceptions

This is the myth that will not die, because a ram really does lift water with no fuel and no electricity visible anywhere. What it is not doing is creating energy. It takes a large flow falling a little and converts it into a small flow lifted a lot, and it pays for that conversion by dumping most of the water it took. Energy out is always less than energy in; the physics page does the accounting for a real example.

The tell is the arithmetic: a ram delivering its full quota of water at a high lift would violate conservation of energy, and no measured ram has ever come close. What looks like a miracle is a very good energy converter that happens to spend its fuel in the form of spilled water, where nobody notices it being consumed.

A ram's appetite is small. Domestic and small-village systems commonly run on a few litres per second, and a ram will beat with a good deal less if the fall is decent — see the performance data for delivered flow per litre of drive flow.

What actually matters is the product of flow and fall. A modest stream with a steep drop will out-pump a large river on flat ground, and a small stream that flows reliably all year is worth far more than a big one that dries in summer. Reliability of the low flow beats magnitude of the peak — which is the whole argument of the source assessment page.

Rams work from roughly 0.5 m of fall and become genuinely useful at a metre or more. What a small fall costs you is not feasibility but output: pumping power scales with the fall, so every extra metre multiplies the water you get.

The related myth is that a small fall forces a small lift. It does not — it forces a low lift ratio. The constraint that matters is h / H, which is why a 1 m fall lifting water 4 m is unremarkable and a 1 m fall lifting it 30 m is a trickle.

There is no hard wall, but there is a steep and effective one. Delivered flow falls roughly in inverse proportion to the lift ratio, so raising the delivery point from 6× the fall to 12× halves the water you get for the same drive flow. Past about 6:1 output becomes sensitive and tuning fragile; beyond about 10:1 it is usually pointless.

None of that is a limit of the machine — it is the lift ratio reasserting itself, and it applies to every energy-converting pump in existence. If you need a very high delivery point, you need more fall, not a cleverer ram.

Low maintenance, yes. No maintenance, no. Two moving parts still move — roughly thirty million times a year — and they wear, along with the seats they strike. Add the intake screen, which blocks, and the air chamber, which slowly loses its cushion and needs recharging.

The honest framing is that a ram needs occasional, brief, local attention rather than none: clearing a screen, renewing a valve rubber, re-charging the chamber. That is a different thing from being maintenance-free, and it is why the operation arrangements matter as much as the pipework.

Often it is surprisingly close, which is the kernel of truth in the claim. The differences are not mainly about efficiency but about consistency, tuning range and — above all — spares. A well-built fittings ram can match a factory unit at small scale; it will not match it for repeatable performance, and it will not have a parts channel behind it.

The decision is genuinely situational and is set out properly on Buy or build. Neither answer is universally right.

Most of the water is spent, which is not the same thing. The spill from the waste valve returns to the channel and is available downstream — indeed it can drive a second ram lower down the hill, as described on Cascades.

What the ram is genuinely poor at is volumetric efficiency: as a fraction of the drive flow, the delivered water is small, often around a tenth at practical lift ratios. If your measure of success is "how much of this stream ends up in my tank", a ram will disappoint you. If it is "how much water can I lift uphill forever for free", it will not.

It will run, for a while, and then it will erode itself from the inside. Silt and grit scour valve seats and check-valve faces at every beat, and the damage is cumulative and irreversible. Air entrainment from a poorly designed intake is just as damaging to performance, cushioning the slam until the machine stops working properly.

A ram wants the same things as any hydraulic machine: reasonably clean water, no air in the column, and an intake that stays clear. Where the water is genuinely dirty, the answer is a settling forebay — or a separation arrangement that keeps the dirt on the drive side, as discussed in the case studies.

A bigger ram passes a bigger drive flow, but the output is set by the drive flow and fall you actually have, not by the size of the machine bolted to them. Fit a large ram to a small stream and it will sit there labouring, never reaching the velocity that slams the waste valve properly — a common and discouraging result.

Size the ram to the flow, then size the drive pipe to the ram. The procedure is on Design & Sizing, and the sizing calculator will tell you the drive-pipe bore it expects.

A ram will run for years with almost no attention, which is where this belief comes from. But it also relies on a stream whose flow varies, an intake that collects debris, a chamber that slowly waterlogs, and a foundation that can be undermined — and it will be someone's job to notice.

The schemes that last are the ones where that "someone" is a named person with a spares kit and a small maintenance fund. The machinery is easy; the arrangements are what need designing.

No. A ram's energy comes from water falling, and still water has none to give. A pond at the same level as the ram will not drive it, and no amount of pipework or tuning will change that.

The same applies to the popular idea of a closed loop: use a ram's own delivery to feed its intake and pump forever. It is a perpetual-motion machine with extra plumbing, and it will stop as soon as the losses exceed the head available. Flat sites need a different technology — see the comparison table on Costs.