How to Read a Sewerage Interpretation Plan (SIP) in Singapore — A Homeowner’s Guide

SIP Plan (Sample)

Thinking of rebuilding or extending your landed home? One of the most important yet misunderstood documents is the Sewerage Interpretation Plan (SIP). This plan directly affects your house layout, costs, and even construction sequence — yet many homeowners only look at it after OTP is signed (big mistake!).

This guide breaks down how to read an SIP, what to look for, and why it matters.

1. What Is an SIP?

The SIP is a technical drawing issued by PUB, showing the location, depth, and size of public sewer lines and ICs (inspection chambers) within and near your property. It helps builders and Qualified Persons (QPs) determine:

• Where your home can be built or extended

• Whether a new sewer connection is needed

• If a reinforced concrete (RC) sewer trench is required

• Whether minimum setbacks from RC structures are met

2. Key Elements to Identify in Your SIP

a. Property Boundary

Usually marked in yellow lines.

b. Public Sewer Line

• Appears as solid or dashed lines, labelled with pipe diameter (e.g. R150 / R225).

• Check the depth (in meters) using subtraction.

• Important: Deeper pipes require wider RC trench and greater setbacks.

c. Inspection Chambers (ICs)

• Marked with a circle or square and labelled “IC”.

• Your “last IC” is the most critical — it determines if you can reuse the connection or must apply for a new connection to PUB sewer.

d. Manholes and Public Connections

• Look for arrows showing flow direction.

• Larger manholes may affect setbacks and trenching, especially if they lie within your site boundary.

3. Why This Matters for Home Design

🧱 Setbacks from RC Structures (As per PUB COP)

• If sewer ≤600mm and depth ≤3.0m → Min 1.0m setback from RC footing/slab.

• If sewer ≤600mm and depth 3.0–5.0m → Min 1.5m setback.

• If building over → Must build RC sewer trench.

🛠 When Do You Need an RC Trench?

• Required if sewer passes beneath or near RC structures.

• Must follow PUB’s minimum size:

  
  

  • 1.5m wide if depth >3.5m

  • Includes slab above and side walls for protection

  
  

Or maybe, you do not even have your own sewer connection and to create your own might cost a BOMB!

When Is a New Sewer Connection Needed?

• If your last IC is located outside your site and can’t be reused due to position or design change.

• Requires submission to PUB + LTA (if under public road).

• Adds cost and time due to road opening permits.

4. What to Do as a Homeowner

1. Buy SIP plan from PUB Inlis.

2. Review it during Step 1–2 of your design phase.

3. Always cross-check with your builder to avoid:

   
   

   • Costly trench works

   • Redesigning layout due to sewer conflict

   • Rejection from PUB

Understanding your SIP isn’t just for engineers — it directly affects your budget, layout, and approvals. Bring it up early during your builder engagement, and ensure all setbacks and trench requirements are factored into design.