Streaming API Developer Guide

Getting Started with Streaming API
Code Examples
Client Connection Considerations
PushTopic Events (Legacy)
Working with PushTopics
PushTopic Queries
Event Notification Rules
Replay PushTopic Streaming Events
Filtered Subscriptions
Bulk Subscriptions
Deactivating a Push Topic
PushTopic Considerations
PushTopic Streaming Allocations
Reference: PushTopic
Generic Events (Legacy)
Monitoring Event Usage
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Deactivating a Push Topic

You can temporarily deactivate a PushTopic, rather than deleting it, by setting the isActive field to false.

To deactivate a PushTopic by Id, execute the following Apex code: 
1PushTopic pt = new PushTopic(Id='0IFD0000000008jOAA', IsActive = false);
2update(pt);