What does backflow mean?

[BobbyJoe]

Hi Everyone, what does backflow mean in plumbing terms, what would happen if you had a water backflow problem in your home and how do you prevent it?

Any information would be really appreciated, thank you.

 

[ShaunCorbs]

Drainage or water supply ?

 

[BobbyJoe]

The water supply in my home

 

[rpm]

Back flow is when the water flows back in the opposite direction from where you want it to go.
eg. Water from my basin backflows into my shower tray.

 

[rpm]

The water supply in my home

Care to say more?

 

[rpm]

Would of been easier to keep to one thread mate.

 

[BobbyJoe]

Sorry you're right I should have kept it to one thread

 

[Stigster]

You have to prevent any possibility of stored water getting back into the main and contaminating it. A classic case would be a garden hose with the end submerged in a pond. A contractor does some work on another part of the system, in the road, for instance and foul water could be pulled back into the main without backflow prevention. That's more or less worst case scenario but it must have happened before. Another scenario is a shower head submerged in a bath full of water could have the same problem. That's why you are supposed to fit check valves to a shower connected to the mains and the ring that the shower hose goes through prevents the head being put all the way into a bath.

The gold standard in backflow prevention is the air gap. Taps have to have outlets a certain height above the spillover level of a sink or basin to prevent backflow.

There are many instances where backflow can cause problems in unbalanced supplied to mixer devices too. What is the specific problem you have?