Fast Evacuation Series: Setup & Full Flow

Full Flow: Removing Restrictions

You should always try to achieve full flow when setting up for your evacuation.

Full flow refers to the optimal non-restricted flow path of molecules being removed from a system. To achieve full flow, start by removing all controllable restrictions, including valve cores, system access ports, and any core depressors from your vacuum hoses. These restrictions can reduce flow to as little as 0.2 cfm. Once they are removed, you will allow unrestricted flow of molecules.

Hose with and without Core Depressor

Valve with and without Valve Core

Restrictive Manifolds and Leak Points

Along with removing restrictions, use a manifold-less setup when available to reduce leak points and potential restrictions. Manifolds, although commonly used, have many leak points along with inherently unreliable performance in deep vacuums and are prone to turbulent restrictive flow.

Y-Fittings vs. T-Fittings

When wanting to increase the number of hoses in your setup, using a single machined fitting to increase the number of connections to the system is the most reliable option. Like manifolds, t-fittings fall victim to turbulent flow. This creates flow paths that are directly in opposition to each other. With a y-fitting, the flow paths can merge seamlessly without creating turbulence or restriction. Along with merging flow paths, a y-fitting maximizes the number of large-diameter vacuum hoses able to connect to your vacuum pump.

Y-Fitting vs. T-Fitting Flow Paths

½ in. Speed-Y

Benefits of Large Diameter Hoses

When it comes to hose size, large-diameter hoses are crucial to achieving full flow. There is more friction in the ¼ in. hose compared to a ½ in. diameter hose. Due to the decreased diameter, the molecules come in contact with the inner hose walls more often. The ½ in. hose has more space for air molecules to flow freely without having to come in contact with the inner wall or other molecules. The molecules in the ¼ in. hose are crowded and colliding much more frequently, causing them to travel slowly or even change direction. Although removing all the friction from a full-flow setup is impossible, even with ½ in. hoses, reducing the number of friction points and increasing the space available for the molecules to flow is the best path to fast evacuation.

½ in. vs. ¼ in. diameter hose

MH120006EAK Black Evacuation Hose

Effective Full Flow Setups

At a certain point, attaching more hoses to your pump isn't going to net the same speed increases due to diminishing returns. When working on large systems, this becomes more apparent. By deploying multiple vacuum pumps, you can overcome these diminishing returns. On the other hand, not all systems require multiple pumps or a lot of hoses.

The Drawbacks of a Single-Hose Setup

When evacuating smaller residential systems, using a one-hose setup is a common thought. This isn’t necessarily wrong, but it isn't the most effective setup in terms of full flow.When running a single hose setup, you are only able to pull a vacuum from one side of the system. This takes significantly longer due to the length of the line set some molecules have to travel, assuming that there is no damage to the system components. If the metering device is electronically controlled or damaged, there is a risk the valve will shut, completely cutting off a large portion of the system.

One hose setup

The Benefits of a Two-Hose Setup

A two-hose setup is more effective than a single-hose setup. This setup allows you to pull a deep vacuum from both sides of the system, making the evacuation quicker. It also gives better assurance that you've fully evacuated the whole system, even with a blockage from internal components. If you insist on using a single-hose setup, always attach your vacuum gauge to the opposite side of the system to ensure an accurate micron-level reading with your full-flow setup ready.

Two-Hose Setup

AV760 Full-Range Vacuum Gauge

In the next blog post, we will review how to diagnose a successful evacuation. Read more here.

Fast Evacuation Series// Part 4 - Setup & Full Flow Video: