Drain symbol
Also called Funnel, Tundish
A drain connection empties a line or vessel, often into an open funnel (tundish) leading to the drain system.
What the drain symbol means
A drain connection empties a line or vessel, often into an open funnel (tundish) leading to the drain system.
How it is drawn
A small line down from the pipe with a valve, ending in a funnel shape or marked D.
The drain symbol in each standard
Drawn as on most US-style legend sheets.
German (DIN): Entleerung. See DIN P&ID symbols.
Where you see it on a P&ID
At low points of lines and vessels.
Tag codes
The drain is commonly tagged:
- D
- OD (open drain)
- CD (closed drain)
Tag formats follow the project numbering procedure. For instruments, the letters follow ISA 5.1, explained on the instrument symbols page.
Related symbols
Frequently asked questions
What does the drain symbol look like on a P&ID?
A small line down from the pipe with a valve, ending in a funnel shape or marked D.
What is a drain used for?
A drain connection empties a line or vessel, often into an open funnel (tundish) leading to the drain system. You will find it at low points of lines and vessels.
What tag does a drain have?
It is commonly tagged D, OD (open drain), CD (closed drain). The exact tag format comes from the project numbering procedure and the legend sheets.
Is the drain symbol the same in ISA and ISO?
No. The drain point is shown with the funnel symbol below the line. The ISO 10628-2 registration number is 2040. Always check the legend sheets at the front of the P&ID set.
What is the drain called in German?
Entleerung. On a German R&I-Fließschema it is drawn to DIN EN ISO 10628-2.
- In production since 2014
- Thousands of daily users
- On MODEC FPSO projects since 2016