1. Presentation on Trap Loss
PLUMBING
Presentation on Trap Loss

2. Trap Loss At the end of this session you should be able to :
Explain what is meant by trap seal loss

3. Why does Trap seal loss occur ?
Trap Loss
Why does Trap seal loss occur ?
Trap seal loss occurs when the seal of the trap is lost as a result of poor
practice and by not following the regulations with regard to sanitation
pipework installation.

4. There are three main causes of loss of trap seal:
Trap Loss
There are three main causes of loss of trap seal:
Self siphonage
Induced siphonage
Compression
Each one of these is the result of poor installation work

5. Induced Siphonage
Caused by appliances connecting into a common waste discharge pipe.
This arrangement is not acceptable on primary ventilated stack.

6. Self Siphonage Most common in washbasins and steep sided appliances.
Ensuring the waste pipe is at the correct length and fall would avoid this problem

7. Compression
Usually caused by discharging W.C. higher than the lowest waste connection.
Use large radius bend at base of stack (min 200mm)
Min 450mm between invert of the drain and lowest branch waste pipe.

8. Trap Loss prevention
Anti siphon trap

9. Maximum pipe runs
Observe these maximum pipe lengths and you shouldn’t have a problem.
Loss of the trap seal can also pose a health hazard.
Appliances
Dia (mm)
Min.trap seal depth (mm)
Max. length of pipe (m)
Pipe Gradient inDeg °
Max Bends No.
Max drop (H) m
Washbasin or bidet
32mm
75mm
1.7m
2.2
40mm
3.0m
1.8 to 4.4 2
Bath or shower
50mm
No limit
1.8 to 9.0
1.5
Bowl urinal
1.8 to 1.9
Trough urinal
Kitchen sink
Dishwater or washing machine
1.8 to 1.4
W.C.
110mm
1.8 min

10. Session Summary We discussed what the causes of trap loss are.
Looked at each of the causes of trap loss.
How to rectify the problem of trap loss.