Airlock forming in water pipe from the overhead tank

[RaviBanthia]

Hi folks,

I have a problem with an airlock forming every time the overhead tank becomes empty.

Even when I fill the overhead tank to the brim, the water in the household outlets comes at a very low speed.

By experimenting, I found that there are two ways to fix the problem each time there is an airlock:

1) Go to the roof of my house and open a tap in the main pipe that distributes water to the whole house.

2) Flush a commode (on the ground floor) that has a manual valve with a large water outflow.

There is an air vent (T-type) installed in the pipe just after the water tank, but the airlock is still forming.

Once, I have removed the airlock using one of the two methods I have listed above, water flows in all the pipes in the house at a decent speed.

My overhead tank is unfortunately not easily accessible (as the stairs to that part were not built).

So I am trying to understand the reason for the airlock forming before calling a plumber.

Also, I am in a town that does not seem to have expert plumbers (or maybe in my 11 year stay, I haven’t found the right person).

It would be immensely helpful if I could get some pointers to I can request the plumber to locate and resolve the problem.

Thank you.

 

[ShaunCorbs]

Sounds like you need a bigger tank

 

[RaviBanthia]

Thank you, Shaun.

I have a 500 liter (132 gallons) tank, which is the most common one here for one- or two-stor(e)y houses.

My house is single stor(e)y, and the tank is about 10 feet above the roof. The base of the roof is about 12 feet above the ground level.

Could the problem be due to the pipe (emerging from the tank) being not level but inclined upward (a little)?

Or could it be due to some minor clogging in the pipe exiting from the tank?

 

[ShaunCorbs]

Should drop from the tank etc shouldn’t rise

 

[RaviBanthia]

Yes, it should fall (or be level, at least).

Could even a small rise cause the problem?

The junction where the horizontal exit pipe (from the tank) turns vertically downwards, could that be where the airlock occurs?

The water level in the tank (when full) is some 4 to 5 feet above that junction.

 

[ShaunCorbs]

Yes a rise could be a problem

 

[RaviBanthia]

Thank you, Shaun.

I’ll have the plumber check the inclination of the exit pipe.

Also, I’ll ask him to check if the air vent itself is clogged.