Sumi Soaker Mark II Water Pressure & Flow Guide

Sumi Mark II is a mist irrigation tube designed for low-pressure water supplies. When connected to water at its operating pressure, it sprays a fine mist from laser-cut orifices along its entire length — covering up to 13 feet of bed width from a single line of tubing.

Mark II's defining advantage is that it requires very little pressure and very little flow. It operates at pressures as low as 3 PSI and draws a fraction of the water that wider-coverage tubing needs. This makes it the most forgiving Sumi product for growers connecting to garden hoses, gravity-fed tanks, low-output well pumps, or any water supply that can't deliver high pressure or high volume.

This guide explains what Mark II requires, what your water supply likely delivers, and what to expect when you connect the two.

Pressure — The Force That Creates the Spray

Pressure is the force pushing water through the tubing and out the orifices. It's measured in PSI (pounds per square inch). Higher pressure pushes water out harder and farther, producing a wider spray pattern.

Mark II is designed to operate at 11.6 PSI (0.08 MPa) at its rated maximum. But unlike many irrigation products, Mark II functions across an exceptionally wide pressure range — from as low as 2.9 PSI (0.02 MPa) up to 11.6 PSI. This means it works with almost any water source that produces flowing water.

Pressure determines three things about Mark II's performance: how wide the spray reaches, how fine the mist droplets are, and how evenly water distributes across the spray width.

Flow — The Volume of Water Feeding the Tubing

Flow is the volume of water your supply delivers per minute, measured in GPM (gallons per minute). Every foot of tubing releases water simultaneously, so longer tube runs need more total flow.

Mark II's flow demand is low — approximately 0.036 GPM per foot of tubing at rated pressure. That's roughly one-quarter of what R-Wide requires for the same bed length.

Here's what that means in practice:

• A 25-foot bed needs about 0.9 GPM
• A 50-foot bed needs about 1.8 GPM
• A 100-foot bed needs about 3.6 GPM
• A 330-foot bed (full roll) needs about 11.9 GPM

These numbers are remarkably low. A typical kitchen faucet delivers 2–3 GPM. Any functioning garden hose delivers far more than Mark II needs for a single bed.

Why Mark II Needs So Little

Mark II operates at roughly one-third the pressure of R-Wide, so the water exits the orifices at lower velocity and volume. It also sprays a narrower pattern (13 feet vs. 33 feet), which means less total water leaving the tubing per foot. The combination of lower pressure and narrower coverage means Mark II sips water where R-Wide gulps it.

The Rated Operating Point

Mark II performs at its published specifications when supplied with 11.6 PSI and sufficient flow. At this point, you get approximately 13 feet of spray width, consistent coverage from inlet to tail on runs up to 330 feet, and the steepest spray angle (80°) — which helps water clear tall crops before arcing down onto the bed..

The Operating Range

According to the manufacturer (Sumika), Mark II operates across a pressure range of 0.02 to 0.08 MPa — that's roughly 2.9 to 11.6 PSI. Performance scales with pressure, but the tubing remains functional across the entire range:

At 11.6 PSI (full rated): spray width is approximately 13 feet total, flow rate averages about 0.34 L/min per meter at 100m runs, and the tubing can run up to 330 feet per line.

At roughly 7 PSI (mid-range): spray width narrows to approximately 8–10 feet total, flow rate decreases proportionally, and coverage remains effective for narrow bed layouts.

At roughly 3 PSI (minimum): spray width narrows to approximately 4–7 feet total, flow rate drops to about 0.13 L/min per meter at 100m. The tubing still sprays — this is not a failure point, but coverage is concentrated close to the tubing line.

Below 3 PSI, the spray pattern becomes unreliable. Water may drip rather than mist from the orifices.

Flow Rates by Run Length

Sumika provided flow rate data at different run lengths. At rated pressure (0.08 MPa / 11.6 PSI):

• 30-meter runs (100 ft): 0.48 L/min per meter
• 50-meter runs (165 ft): 0.44 L/min per meter
• 100-meter runs (330 ft): 0.34 L/min per meter

Flow per meter decreases on longer runs because friction inside the tubing reduces pressure toward the far end. This is normal and expected — the tubing is engineered to compensate for it within its rated run length.

At minimum pressure (0.02 MPa / 2.9 PSI), flow drops significantly:

• 30-meter runs: 0.20 L/min per meter
• 50-meter runs: 0.18 L/min per meter
• 100-meter runs: 0.13 L/min per meter

Even at minimum pressure on a full 330-foot run, total flow demand is only about 1 GPM. Nearly any water source can deliver that.

The Pressure Regulator's Role

Most water supplies deliver pressure well above 11.6 PSI. A garden hose bib typically runs 40–60 PSI. A municipal mainline runs 50–80 PSI. This excess pressure would overdrive the spray pattern — too much pressure causes the mist to break into large droplets and overshoot the intended bed width.

The pressure regulator (a Senninger PMR-MF preset to 12 PSI) sits between your water supply and the Mark II tubing. It reduces your incoming pressure to 12 PSI, regardless of how high your supply pressure is. It's included in every Mark II system kit.

The regulator requires your incoming pressure to be at least 17 PSI — that's 5 PSI above the 12 PSI outlet setting. Below 17 PSI, the regulator can't maintain its outlet pressure reliably.

The regulator also has a maximum flow capacity of 20 GPM. Given Mark II's low flow demand, you would need to run more than five simultaneous 330-foot beds to hit this limit — a scenario most market gardeners will never encounter.

When You Don't Need the Regulator

If your water supply naturally delivers pressure between 3 and 12 PSI — common with gravity-fed tanks, rain catchment systems, or very low-pressure well setups — the regulator would only reduce pressure you can't afford to lose. In this case, connect Mark II directly to your supply with an 80-mesh inline filter (to protect the tubing from debris). The tubing will operate at whatever pressure your supply provides.

Garden Hose Connected to an Outdoor Spigot

This is the simplest and most common setup for Mark II users. A garden hose connects your outdoor faucet to the Mark II tubing through the Garden Hose Connector (which includes the pressure regulator).

What it typically delivers: 5–12 GPM at 40–60 PSI.

Mark II on a 100-foot bed needs only 3.6 GPM. Even the weakest garden hose setup delivers more than this. A garden hose is essentially unlimited capacity for Mark II — you could run multiple beds simultaneously without any concern about flow.

Pressure is a non-issue. Any garden hose bib delivers far more than the 17 PSI the regulator needs at its inlet.

Realistic expectation: a garden hose setup supports Mark II at any bed length, any number of simultaneous beds (up to the regulator's 20 GPM limit), with full rated performance. This is the easiest product to supply with water.

Poly Tubing Mainline with a Pump or Municipal Connection

For growers with dedicated irrigation infrastructure, Mark II connects through the Mainline Connector (which includes the pressure regulator with pipe thread fittings).

Even the smallest mainline comfortably supports Mark II:

• 1/2-inch poly (4.4 GPM capacity): supports one Mark II bed up to 120 feet, or multiple shorter beds
• 3/4-inch poly (8.2 GPM capacity): supports multiple 100-foot beds simultaneously
• 1-inch poly (13.8 GPM capacity): supports nearly any Mark II configuration

Pressure is rarely a concern on mainline systems. Even after friction loss over long pipe runs, most mainline setups deliver well above the 17 PSI the regulator needs.

Well Pump Systems

Mark II is well-suited to low-output well pump systems that might struggle with higher-demand tubing.

A 1/2 HP well pump delivering 4–6 GPM can run a single Mark II bed at any standard length with flow to spare. A 1 HP pump delivering 10+ GPM can run multiple Mark II beds simultaneously.

If your well system runs at low pressure (30/50 PSI tank settings), you have more than enough inlet pressure for the 12 PSI regulator after accounting for friction loss.

Gravity-Fed and Rain Catchment Systems

This is where Mark II truly shines compared to other irrigation products. Gravity-fed systems often deliver only 2–10 PSI depending on tank elevation and pipe size. R-Wide requires a minimum of 14.5 PSI to spray — ruling out most gravity setups. Mark II operates down to 3 PSI.

A tank elevated 7 feet above the tubing produces roughly 3 PSI through gravity alone (0.43 PSI per foot of elevation). That's enough for Mark II to spray at minimum width. A tank at 20 feet produces about 8.7 PSI — well within Mark II's effective operating range.

For gravity-fed systems, skip the pressure regulator (it would eat pressure you need) and connect Mark II directly with an 80-mesh filter. The tubing will spray at whatever pressure gravity provides.

Full rated pressure and flow (11.6 PSI, sufficient GPM)

The regulator holds at 12 PSI. Spray width reaches the full 13 feet. Coverage is even from inlet to tail. Precipitation rate is approximately 0.20 inches per hour. This is the ideal scenario.

Adequate pressure, marginal flow

This scenario is rare with Mark II because its flow demand is so low. But if you're running many simultaneous beds through a very restricted supply, internal pressure may drop along the runs. The inlet end sprays normally; the far end narrows slightly. Still effective irrigation — just not perfectly uniform.

Reduced pressure (3–11 PSI, no regulator)

The tubing operates in its extended range. Spray width is narrower — perhaps 7–10 feet at mid-range pressure, or 4–7 feet at the minimum. The 80° spray angle still directs water upward before it arcs down, which helps clear tall crop canopy even at reduced width. Coverage is concentrated closer to the tubing line, which may actually be ideal for narrow bed layouts (24–30 inch beds).

If your beds are 30 inches wide, even a 4-foot spray width covers the bed surface with some overlap. This is a workable configuration for many market garden layouts.

Very low pressure (under 3 PSI)

The spray pattern becomes inconsistent. Some orifices may drip rather than mist. If your gravity system can't maintain 3 PSI at the tubing inlet, consider raising the tank height or reducing the supply line length to cut friction losses.

Step 1: Estimate Your Available Flow

For most Mark II setups, this step is a formality — nearly any water source exceeds Mark II's needs. But if you want to confirm:

Turn on your water supply fully, hold a 5-gallon bucket under the outlet, and time how long it takes to fill.

GPM = 5 ÷ (seconds ÷ 60)

Example: 30 seconds = 10 GPM. Example: 60 seconds = 5 GPM. Example: 120 seconds = 2.5 GPM.

Even 2.5 GPM supports a single Mark II run on beds up to about 70 feet.

Step 2: Calculate Your Demand

Multiply your bed length in feet by 0.036. That's your GPM demand per bed at full rated pressure.

• 25-foot bed: 25 × 0.036 = 0.9 GPM
• 50-foot bed: 50 × 0.036 = 1.8 GPM
• 100-foot bed: 100 × 0.036 = 3.6 GPM

If you want to run multiple beds simultaneously, multiply by the number of beds. Four 100-foot beds at once need 14.4 GPM.

Step 3: Compare Supply to Demand

If your available GPM exceeds your demand — which it almost certainly does — you're in good shape.

If running many beds simultaneously, check that your total demand doesn't exceed the regulator's 20 GPM capacity. If it does, run beds in groups (zones) rather than all at once.

Step 4: Check Your Pressure

For garden hose and mainline users: your supply pressure exceeds the 17 PSI regulator minimum. No action needed.

For gravity-fed systems: calculate your available pressure by multiplying your tank height (in feet above the tubing) by 0.43 PSI per foot, then subtracting friction loss in your supply pipe. If the result is above 3 PSI, Mark II will spray. If it's above 17 PSI, you can use the regulator. If it's between 3 and 17 PSI, connect directly without the regulator.

Mark II is the right choice when any of these apply:

Your water supply is limited. Garden hose with weak pressure, small well pump, gravity-fed tank, or long supply runs with significant friction loss. Mark II works where R-Wide can't.

Your beds are narrow. If your beds are 30 inches wide or less, Mark II's 13-foot spray width covers them with plenty of overlap. R-Wide's 33-foot width would overshoot the bed and waste water in the pathways.

You have tall crops. Mark II's 80° spray angle is significantly steeper than R-Wide's 35°. This means the water shoots upward before arcing down, clearing tall plants that would intercept R-Wide's flatter trajectory. If your crops exceed the height that R-Wide can clear at your pathway width, Mark II is the solution.

You want to run many beds simultaneously. Because Mark II uses roughly one-quarter the flow per foot, your water supply can feed four times as many Mark II beds as R-Wide beds at the same time.

You're on a gravity-fed system. Mark II's 3 PSI minimum operating pressure means a tank elevated just 7 feet can power it. R-Wide needs a minimum of about 15 PSI — requiring a tank at 35 feet or a pump.

Mark II Rated Specifications (at 11.6 PSI / 0.08 MPa)

• Spray width: 13 feet (approximately 6.5 feet per side)
• Flow rate: 0.036 GPM per foot of tubing
• Precipitation rate: approximately 0.20 inches per hour
• Maximum run length: 330 feet (100 meters)
• Recommended tube spacing: 10 feet between parallel lines
• Spray angle: 80° (steep — clears tall crops)
• Maximum spray height: 79 inches (at rated pressure)
• Recommended filtration: 80 mesh

Flow Demand by Bed Length

Operating Range (Manufacturer Confirmed)

Pressure Regulator Requirements

• Preset outlet: 12 PSI
• Minimum inlet pressure: 17 PSI
• Maximum flow: 20 GPM per regulator
• Included with all Mark II system kits

What Your Supply Can Typically Handle

Use our free online tools to get a personalized recommendation:

Sumi Soaker System Planner — Tells you what tubing and how many rolls you need based on your bed layout.

Sumi Soaker Water Supply Calculator — Tells you whether your water supply can handle the setup you need, and what to do if it can't.

Both tools are available at shop.moderngrower.co.

Questions? Email us or use the chat on our website. We'll walk you through it.

The Sumi Soaker R-Wide and Mark II are available in the US from Modern Grower. Visit shop.moderngrower.co to see the full product line, starter kits, and accessories.

Ready to figure out what you need? 

Use our System Planner to size your setup and our Water Supply Check to verify your pressure and flow. Or reach out to us directly at hello@moderngrower.co or 877.850.1555 — we're happy to help you design a system that fits your layout.