Check Valve

[luudee]

 

BTW, what should be the ideal air pressure of the pressure tank ?

 

Mine is set to the desired pipe pressure (e.g. pressure switch setting).

Is that correct ?

 

I actually have a Grundfos pressure tank in the back of the garage, I

got it a couple of years back with the intention to replace the cheese

made one. But so far the Chinese made one is holding up, I was given

6 months warranty on it at it has been almost two years now, lol ... no

water coming out of the air valve yet ...

 

Thanks,

rudi

[Pib]

Usually it's set to 2 psi below the pump cut-in pressure....whatever pressure the pump turns on at.

 

http://inspectapedia.com/water/Water-Tank-Bladder-Pressure-Adjustment.php

 

[sipi]

31 minutes ago, Pib said:

Usually it's set to 2 psi below the pump cut-in pressure....whatever pressure the pump turns on at.

 

http://inspectapedia.com/water/Water-Tank-Bladder-Pressure-Adjustment.php

 

From Rudies photo of his Danfoss differential switch. Pressure is set at 300kPa/ 45psi. Diff is 70 kPa/ 10psi. So cut in is 230kPa/ 35psi.

Pressure tank set at 33psi?

[luudee]

1 hour ago, sipi said:

From Rudies photo of his Danfoss differential switch. Pressure is set at 300kPa/ 45psi. Diff is 70 kPa/ 10psi. So cut in is 230kPa/ 35psi.

Pressure tank set at 33psi?

 

Yep, that's what I have it set for !

 

Thanks guys !

 

rudi

[sipi]

13 minutes ago, luudee said:

 

Yep, that's what I have it set for !

 

Thanks guys !

 

rudi

Sipi knows more about bum guns and bed pans than pressure tanks. 

Maybe someone can explain the logic of setting it below cut in pressure. 

[sipi]

My logic would be that if is set below the low pressure cut in then the bladder is permanently inflated and has no room for expansion. 

If it were set at 47 psi (2 psi) above the normal operating pressure then the bladder is deflated and can absorb any hydraulic shock.

That is purely my logic knowing nothing about them. I hope someone can explain better.

[grollies]

45 minutes ago, sipi said:

Sipi knows more about bum guns and bed pans than pressure tanks. 

Maybe someone can explain the logic of setting it below cut in pressure. 

@Naam is the one for bum guns, his is at 3 barg. Hope he clenches when spraying...

[sipi]

12 minutes ago, grollies said:

@Naam is the one for bum guns, his is at 3 barg. Hope he clenches when spraying...

I need to connect mine to a warm water mixing valve.

Those cold mornings.....

[Pib]

2 hours ago, sipi said:

My logic would be that if is set below the low pressure cut in then the bladder is permanently inflated and has no room for expansion. 

If it were set at 47 psi (2 psi) above the normal operating pressure then the bladder is deflated and can absorb any hydraulic shock.

That is purely my logic knowing nothing about them. I hope someone can explain better.

It boils down to keeping the right balance of water and air in the tank to allow proper draw-down capability....draw-down being where water is push out of the tank without the pump needing to be running.

 

And also in a "captive air" type tank (i.e., one with a bladder) and depending on the location of the pressure switch  if the tank air pressure is too high the pump possibly can't even turn on as the pressure is always above pump cut-in pressure....in a non-captive air tank this problem would automatically correct itself when first opening a tap as over-pressure air would escape that router.

 

Many tanks do not have bladders (i.e., non-captive air tank)...there is no material such as rubber that separates the water and air....nothing to keep the air from very slowly being absorbed into the water within the tank causing a waterlogged condition.  The Mitsubishi and Hitachi pumps which set on top of a small pressure tank (probably the most common water pump used in Thailand) does not have a bladder to keep the water and air separated.  But they do have an air balance control valve that keeps the proper amount of air in the tank by allowing a very small amount of air to enter the tank to offset air that is naturally absorbed by the water.  

 

On large standalone pressure tanks not using a bladder a separate air balance value is needed to ensure additional air is added as needed; otherwise you must frequently monitor the air pressure and add pressure to offset the air loss....and even completely drain the tank sometimes to ensure the pressure gauge is measuring air versus water....like in a waterlogged tank....and ensure you have to proper proportion of air to water in the tank.

 

But it boils down to maintaining the proper draw-down capability.... and for a captive air tank (has a bladder or diaphragm to keep the water and air separated to allow the pump to turn on a required cut-in pressure.

 

I wonder if Rudi's tank is maybe really waterlogged or almost waterlogged.  If his pump always turns on with even a small amount of water being drawn then it's waterlogged.   If it don't turn on and will push out X-amount of liters of water before the pump turns on then it's not.

[luudee]

On 5/20/2017 at 7:36 PM, Pib said:

It boils down to keeping the right balance of water and air in the tank to allow proper draw-down capability....draw-down being where water is push out of the tank without the pump needing to be running.

 

And also in a "captive air" type tank (i.e., one with a bladder) and depending on the location of the pressure switch  if the tank air pressure is too high the pump possibly can't even turn on as the pressure is always above pump cut-in pressure....in a non-captive air tank this problem would automatically correct itself when first opening a tap as over-pressure air would escape that router.

 

Many tanks do not have bladders (i.e., non-captive air tank)...there is no material such as rubber that separates the water and air....nothing to keep the air from very slowly being absorbed into the water within the tank causing a waterlogged condition.  The Mitsubishi and Hitachi pumps which set on top of a small pressure tank (probably the most common water pump used in Thailand) does not have a bladder to keep the water and air separated.  But they do have an air balance control valve that keeps the proper amount of air in the tank by allowing a very small amount of air to enter the tank to offset air that is naturally absorbed by the water.  

 

On large standalone pressure tanks not using a bladder a separate air balance value is needed to ensure additional air is added as needed; otherwise you must frequently monitor the air pressure and add pressure to offset the air loss....and even completely drain the tank sometimes to ensure the pressure gauge is measuring air versus water....like in a waterlogged tank....and ensure you have to proper proportion of air to water in the tank.

 

But it boils down to maintaining the proper draw-down capability.... and for a captive air tank (has a bladder or diaphragm to keep the water and air separated to allow the pump to turn on a required cut-in pressure.

 

I wonder if Rudi's tank is maybe really waterlogged or almost waterlogged.  If his pump always turns on with even a small amount of water being drawn then it's waterlogged.   If it don't turn on and will push out X-amount of liters of water before the pump turns on then it's not.

 

Thanks for all the information.

 

In my system, it does take some time/draining before the pump starts up again. And

it takes a little while after the tab is closed for the pump to turn off, as it is building up

pressure. I am not sure if my current tank has a membrane, but I assume it does. The

Grundfos tank that I am planning to install one day definitely has one ...

 

rudi