Swimming pool Multivalve and system pressure

[stillhere]

Hi out there

I have an overflow pool controlleds by a Multivalve selector.

When in normal overflow mode the pressure in the system is ok. However yesterday when I switched to backwash / rinse modes, the pressure went to zero and no water passed out of the system ( to the backwash tank ).

Does anyone have a suggestion as to the problem, or wouls I be better just replacing the Multivalve Unit?

Thanks


Joe

 

[duraleigh]

Joe,

Welcome to the forum.

I can usually figure out these flow issues but yours has me stumped.

A pressure of zero means no water is passing thru the filter which means you have blocked off the suction side of the pump by turning the multiport valve.......I cannot envision a circumstance where that can happen.

If the multi-port is blocked, your pressure would go to max (35 psi or so).

What is your normal psi in "filter" (overflow) position?

 

[stillhere]

Hi Dave

Thanks for the reply. The pool was built 2 years ago, and the pressure on the guage on top of the filter tank has always been 0.5 Bar ( about 15 psi? ) the bottom of the green. Some peole I know with the same system have always operated on ahigher pressure but as my system worked fine, I just left well alone.

The multivale has 6 selections Filter, Backwash, Rinse, Recirculate, Waste, Circulate. The pressure is normal ( 0.5 Bar ) in the filter position. Backwash, rinse and Waste the pressure drop to zero. As part of the mutivalve housing there is a inspection chamber, cylindrical clear plastic 3 inches, so that when you backwash you can see the dirty water clearing out the system. This is now showing 3/4 full of water. Never seen it like that before. Hope you can help.

Thanks

Joe

 

[duraleigh]

This is now showing 3/4 full of water. Never seen it like that before.

That helps. Air is certainly getting into the system which would account for the 0 psi.

The pump strainer basket should likewise be filled or partially filled with air as well. Yes?

It may be possible that when you switch the multiport, you are losing prime in the pump. If that's the case, letting the pump run for a minute otr so (not much more than that) should reprime the pump and the psi go back to normal.

You may have a problem with a vacuum breaker on the backwash line but let's confirm that the pump is losing prime first and then address why.

 

[stillhere]

Hi Dave

Went to try out your suggestion. I had the pool on 'circulate'. Switched the main drain to close and opened the ballast tank valve. When I did this I could hear water running from the ballast tank and saw the water level in the ' rubbish basket ' come up almost to touch the perpex cover. Then switched mutivalve to backwash. The pressure immediately came up to the 0.5 Bar. Gave it a minute and then checked the backwash holding tank. There was water in the tank, about 3 inches over the bottom of the two ton tank.

Switched back to normal filter mode on the multivalve. However.... I can't see any water in the rubbish basket. As the ballast tank valve is open, should the basket fill up with water?

Regards

Joe

 

[duraleigh]

Joe,

I can't follow your terminology. Where do you live?

The key to see if you are losing "prime" is the pump strainer basket...located in front of the pump where the water comes into the pump....normally has a see-thru lid.

If, at all times, that basket is not full of water, you have allowed air into the system. (losing prime)

The names of some of your equipment escape me but it sounds more and more like you are losing prime and will need to figure out a way to switch positions on your multiport without letting air into the system.

 

[stillhere]

Hi Dave

I live in Cyprus at the moment. (Although I am from the UK.)

I went out and checked the basket again to see if there was a blockage anywhere but found that the water was full. Looking through the plastic cover I thought the water was low. My mistake.

Anyway since you explained about repriming the pump I have got pressure back again in all multivalve selection modes. So looks like a solution to me.

Thanks for your help.


Joe

 

[stillhere]

Lack of Pressure
Last asked this question some months ago but problem is back! Dave if you are still around, I do seem to be getting air into the system, and the problem seems to be when I am in normal overflow filter mode i.e. the valve to ballast tank is open and inlet open. I don't seem to have a problem when I am in circulation mode i.e. main drain valve open and inlet valve open.
The water in the ballast tank has never to my knowledge been low enough to reach the outlet pipe.
Today I had no pressure showing when I was in normal overflow filter mode. I then switched to circulation and the pressure came back. Left it to run for an hour then changed back to normal overflow mode and the pressure was okay. How is air getting into the system?

Joe