Simple Pump Model 100 (100CA cylinder)

What these numbers mean for an off-grid build

The table above is what the manufacturer publishes. This section is what those figures imply once the unit is doing real work, worked from this row and from the 17 products in the same table. The arithmetic is shown so you can check it against your own design rather than take it on trust.

Head, and where the pump can sit

Maximum head is 325 feet, meaning the vertical lift plus friction losses the pump can overcome before flow stops. Friction in the pipe run counts against that budget, so a pump lifting from a deep static level through a long horizontal run has less margin than the raw number suggests.

Shutoff pressure is listed at 45 psi, which corresponds to roughly 104 feet of head, since one pound per square inch lifts water about 2.31 feet. That equivalence is worth remembering when a system mixes pressure ratings and elevation figures, which most do.

Where this type fits

Listed as hand pump. Submersible pumps sit in the water and push, which works at depth and is the usual answer for a drilled well. Jet pumps sit at the surface and pull, which is easier to service and limited in lift. Diaphragm pumps are the common choice for pressurizing a cabin from a tank. Solar direct pumps run straight from panels with no battery, pumping whenever the sun shines into storage that provides the buffer, which is a resilient arrangement and slow by design.

Whichever type you choose, keep a spare of whatever is hardest to obtain and record the model and fittings in your systems binder. A pump failure in winter is a bad time to be learning the procedure. The spares reference lists what to hold for each system.

How this fits with the rest of the system

A pump is chosen against the well or tank on one side and the electrical system on the other. Lift and flow have to suit the source; startup current and running draw have to suit the inverter and the cable. The inverter table lists surge ratings, which is the figure a motor start tests.

Where the source is a low-yield well, the right answer is usually a slower pump filling storage over hours rather than a powerful one meeting demand directly, which changes both the pump choice and the plumbing. The well pump calculator works the lift and flow, and lesson three covers the storage and freeze protection that go with it.

Checking these figures against the datasheet yourself

Check whether maximum flow and maximum head are quoted at the same operating point, because they are usually not: flow falls as head rises, and the useful figure is the curve rather than either endpoint. Confirm whether the amperage quoted is running or locked-rotor, and note the duty cycle, since some diaphragm pumps are not rated for continuous operation.

Two conventions catch people out across every category. The first is that a specification quoted without its test conditions is not really a specification, so where a datasheet gives a number and no conditions, treat it as marketing until you find the conditions. The second is that model names persist across silent revisions, so a sheet downloaded three years ago may not describe the unit in the box. The price index and the observed prices above are dated for the same reason.

Installing it, and living with it afterwards

Surface installation makes servicing straightforward and puts the limits on suction lift instead. Keep the pump close to the water level, keep the suction line short, airtight, and properly primed, and protect the unit from freezing, since a surface pump is the first thing in the system to burst in a cold snap.

Whatever the type, fit a pressure switch and a suitably sized pressure tank so the pump is not short-cycling itself to death, protect against dry running, and put a union either side of the pump so it can come out without cutting pipe. Record the model, the fittings, the wire size, and the setting depth in your systems binder, and keep the spares that are specific to it on the shelf. In winter, a pump failure is not the moment to be working out which parts you need.

What separates one pump from another

Pumps are chosen by the shape of the job rather than by a single rating, and the specification that decides everything is the curve of flow against head rather than either figure alone.

Start with the source. A drilled well at depth calls for a submersible; a shallow source or a tank suits a surface or jet pump; a cabin pressurized from storage usually wants a diaphragm pump with a pressure switch and tank. A solar direct pump running straight from panels into storage removes the battery from the water system entirely, which is a genuinely resilient arrangement in a place where the pump is the critical component.

Then look at duty. Some pumps are rated for continuous operation and some are not, and a diaphragm pump asked to run all day will not last. Consider whether dry-run protection is built in, since running dry destroys most pumps quickly and a low-yield well makes that a real scenario rather than a theoretical one.

Finally, weigh serviceability against efficiency. The most efficient pump on the table is a poor choice if its parts are proprietary and slow to obtain, because a water outage is the one failure you cannot wait out comfortably. A slightly thirstier pump with common seals, a local supplier, and a spare on the shelf is usually the better off-grid decision.

Storage, pressure, and why the tank matters more than the pump

A pump is only half of a water system. What decides whether the taps behave is the storage and the pressure arrangement behind it, and most off-grid frustration with water traces back to those rather than to the pump itself.

Storage buffers a slow source. A well that recovers at a modest rate can serve a household comfortably if a cistern fills gently over hours and the house draws from the cistern, and it will disappoint badly if the house draws from the well directly. That single design decision often matters more than any specification on this page.

Pressure comes either from elevation or from a pump and a pressure tank. Gravity gives roughly one pound per square inch for every 2.31 feet of height, so a tank on a rise can run a house with no pump at all, which is the most reliable arrangement available. Where a pump is needed, a correctly sized pressure tank is what stops it short-cycling itself to death, and undersized tanks are the most common installation error in owner-built systems.

Keep one path to water that needs no electricity: a gravity feed, stored water, or a hand pump. That principle is covered in lesson ten, and the water usage calculator turns a household into the daily figure the storage has to cover.

Freezing, and the failures that follow

Water expands as it freezes and splits whatever contains it, which makes cold the most destructive thing that happens to a water system. The casualty is rarely the tank, which freezes slowly because of its volume. It is the pipe stub, the pressure switch, the filter housing, or the pump body, all of which can freeze in an hour.

Everything holding water must be below the local frost depth, inside heated space, drainable, or heat traced. Heat trace needs power, so the case to design for is a freeze and an outage at the same time. Bury lines to the depth your county actually uses rather than the depth quoted from somewhere else, slope them so they can be drained, and put the valves where you can reach them in a storm rather than behind the woodpile.

Surface and jet pumps are the most exposed and want an insulated, gently heated pump house with a heat source you can run from the battery bank. Submersibles are protected by depth, but the pitless adapter, the wellhead, and the run into the building are not. Lesson three covers the whole water design in order.

Hand pumps and the no-power fallback

Whatever else a water system has, it is worth keeping one path to water that needs no electricity at all. On a shallow source that means a hand pump; on a deeper one it means a deep-well hand pump designed for the lift, or stored water, or a gravity feed from a tank on higher ground.

This is the cheapest resilience measure in an off-grid house and the one people are most consistently glad of. A pump failure, a controller fault, a dead bank in a dark week, or a generator that will not start on a cold morning all end the same way if the only route to water runs through the electrical system.

Size the fallback for survival rather than for comfort: enough for drinking, cooking, and basic washing for the days it would take to get a part. Then test it, because a hand pump that has never been primed and a tank valve that has never been turned are a plan rather than a backup.

What the table cannot tell you

Every figure above comes from a published datasheet, and datasheets describe a unit under test conditions rather than in your building. They do not tell you how a manufacturer behaves when something fails inside the warranty period, whether spare parts will still be available in ten years, how the firmware behaves in an edge case, or whether the support line is answered by someone who knows the product. Those things decide as much of the ownership experience as the specifications do, and the place to learn them is from people running the equipment: the forum is a reasonable place to ask.

Nor does a datasheet describe the installation. Most off-grid equipment that disappoints its owner was undersized for the real load, wired with conductors chosen by eye, protected by fusing selected on price, or sited somewhere too hot, too cold, or too awkward to service. The equipment rarely fails on its own terms. Lesson six is the one to read before buying anything on this page, and the system planner puts the whole design together so the components are chosen against each other rather than one at a time.

Specifications here are recorded from the manufacturer datasheet or a primary retailer page on the date shown, with a confidence flag on every row. Manufacturers revise datasheets, and models are superseded without changing name. Check the current sheet before you spend money, and if you find a figure here that no longer matches the source, the corrections page is how to tell us; corrections are logged publicly rather than quietly edited. How this site researches sets out the rest.