A.Y. McDonald DuraMAC Dual-Mode Simplex Booster Pump

The Dual-Mode Simplex is the complete package: one pump, a 20 gallon pressure tank, the pressure gauge, the no-lead brass check valve and the piping between them, assembled on a 304 stainless steel base. With up to 70 GPM it is the straightforward choice for a small commercial building, a smaller apartment building, or light industrial and irrigation work where one pump covers the load.

Stainless steel and no-lead brass waterway. Electronics are separated and sealed from the waterway for safety and ease of field repair, with dry-run protection.

Two pumps carry more water and hold more pressure at the flow the building actually draws. The same pump is offered as the Dual-Mode Duplex: two pumps on one stainless base under lead/lag control, to 120 GPM, with either pump able to carry demand alone. The Modular is the same pump without base or tank, for tying into existing piping.

At 70 GPM a single 60 PSI pump adds 10 psi; the Duplex, with both pumps running, adds 41 psi at the same flow, because each pump carries a share of the water and sits higher on its own curve. The 44 PSI pair goes from 19 psi to 33 psi. The shut-off ceiling at zero flow stays at the model’s boost, 60 or 44 psi.

Single-pump figures from the published curve on p. 243; two-pump figures from A.Y. McDonald’s published Duplex curve, both pumps running, p. 245 (Baker Water Systems DuraMAC Booster Pumps catalog, rev 3/26), rounded down. Configuration is chosen at purchase.

The figures below are the pressure this pump adds. That is what a pump curve measures — the impeller does not know what pressure is already on its inlet.

Models

Source: Baker Water Systems DuraMAC Booster Pumps catalog, rev 3/26, p. 243. PRV: A.Y. McDonald recommends a pressure reducing valve above this incoming pressure, so total boosted pressure stays below 80 psi. Many plumbing codes do not recommend system pressure above 80 psi; check local code.

Pressure added in PSI

Drawing from a tank or cistern — nothing arrives with pressure, so what the pump adds is what you get. Read the table straight through: the 60 PSI model delivers about 40 GPM at 39 psi.

Fed by a city main — this is a single-speed pump, so the boost arrives on top of whatever the main already delivers. A.Y. McDonald recommends a pressure reducing valve above 36 psi incoming on the 44 PSI model and above 20 psi on the 60 PSI model, so that total boosted pressure stays below 80 psi.

Best operating range: 30 to 55 GPM. Below this range the pump recirculates internally, which causes vibration and premature seal wear. Above it, it cavitates and the motor draws past its rating. Most booster failures are pumps that were oversized for the building.

Zero flow is the shut-off point — a ceiling, not a working point. The table ends at the published maximum, 70 GPM. Figures are 60 Hz US data at full speed, digitized from the published curve in the Baker Water Systems DuraMAC Booster Pumps catalog, rev 3/26, p. 243, and rounded down. Best operating range is derived from the published curve; A.Y. McDonald publishes no efficiency curve for these models. Points at 10 GPM are left out to keep the table readable; the full curve is in the image gallery. Feet of head = PSI × 2.31.

Same pump, same motor, same dual-mode control in all three. What changes is what comes with it and how much water it carries. You are looking at the Simplex.

Figures from the Baker Water Systems DuraMAC Booster Pumps catalog, rev 3/26, pp. 241–246.

The DuraMAC Dual-Mode control runs in two modes. It is a different control from the three-mode unit fitted to the Residential and Light Commercial boosters.

Pressure Mode — starts on pressure drop, stops on low flow. The control measures pressure with a transducer and starts the pump at an adjustable start pressure point. The pump stops when flow falls below three gallons per minute. A preset seven-second delay after flow stops fully pressurizes the system and eliminates water hammer.

Flow Mode — starts and stops on flow, regardless of pressure. Use it where there is minor leakage or where incoming pressure varies. Starting flow is approximately five gallons per minute; the pump stops when flow falls below three.

Parts in contact with the water, per the Baker Water Systems DuraMAC Booster Pumps catalog, rev 3/26.

Seals, impellers, controls and other service parts for this pump are listed on DuraMAC Booster Pump Parts — 70 GPM Commercial, by part number.