Main drain not working and pump pressure oscillating

[Emile]

Hello,
I am having troube (2 issues) with my swimming pool system.

1- My main drain is not working.
I ran a shaft with a piece of thin rope attached to it to see if there was any succion at the bottom and there is none.
Here is a picture of my pump and filter setup as well as my skimmer basket:




As you can see there is only one hose going to the pump inlet and no valves for selecting main drain. Is the second hole in my skimmer (pool side) going to my main drain?. Should I remove the plug and use a vacuum control plate to divert the succion? Will that get me about 50%-50% succion at the skimmer and at the main drain?

2-When plugging the vacuum hose, the filter pressure oscillates - watch the video I posted on youtube here :

Sometimes the vacuum hose also oscillates back and forth into the skimmer and produces a noise sounding like a duck.

• This only happens when the vacuum hose is plugged in. When unplugged it runs fine.
• The pump was properly primed before plugging in the vacuum hose and having the issue.
• I had my system tested for leaks last Friday, and there are no leaks in the plumbing.
• I just put a brand new Hayward Super Pump.
• I changed the vacuum hose last spring (2018) and there is no hissing sound indicating air intake at the hose level.
• I have properly filled my vacuum hose prior to connecting it to the skimmer control plate at the bottom of my skimmer.

What could possibly be going on ? I am out of ideas.

Thanks !

 

[Texas Splash]

Welcome! For question:
1). I suspect the plugged hole was plumbed to your drain. Is this a new home for you? Was that hole always plugged (if you know)? Sometimes a drain line goes bad (leak) so it gets plugged. If you know it's fine, you should be able to remove the plug. If you don't know, just watch for odd changes if the line went bad before and was plugged on purpose. Pools operate fine without a main drain, so I wouldn't let it bother you too much.
2) Seems like the pump is starving for water & churning. I was going to ask about the pool's water level, but you're vacuuming when it happens. So even though you don't hear hissing, the hose may still have a tiny leak. But you should also check standard areas for suction side air leaks like the pump basket O-ring (lubed) and drain plugs. You might get lucky and it be one of those.

 

[Richard320]

That pump sounds like the vacuum head is getting stuck to the floor and starving the pump. When the pump loses prime, the head releases, the pump reprimes, and the cycle begins. Or maybe the hose is kinking and getting sucked shut. Some air in the basket and a lot of churning in there is normal for me when I vacuum, but I never ever get that surging.

 

[JamesW]

Maybe a clogged vacuum hose.

Do you have a lot of water behind the liner?

 

[Emile]

Welcome! For question:
Is this a new home for you?

Thanks and yes, I've been here for two years but I never removed the plug. It was there when I got the house.

But you should also check standard areas for suction side air leaks like the pump basket O-ring (lubed) and drain plugs. You might get lucky and it be one of those.

It's a brand new pump, so I'm assuming drain plugs and o-ring are fine. I can try adding magic lube.

That pump sounds like the vacuum head is getting stuck to the floor and starving the pump.

I forgot to mention that this is without the vacuum head. So the vacuum hose is loose underwater without the head connected.

Maybe a clogged vacuum hose.

Do you have a lot of water behind the liner?

Yes I do have a lot of water there. What would be the relationship between the hose being plugged and the water behind the liner ?

Also, I made sure my vacuum hose is not plugged by holding it against the return jet. Water seems to flow fine in the hose. I also put the hose on the cement with both ends underwater and watched for water coming out of it while holding an end against a jet and I didn't see any obvious leaks.

 

[LTPOrangePool]

I second what Richard said, how is it when the vacuum is off the floor? That also could be a weak spot or kink in the hose. Under good suction it collapses internally, then starves and spools the pump, which then the hose opens up enough to start the flow and the cycle starts all over again. I've seen this many times with hydraulic systems, tight corners will erode a flap of inner material of the hose and starve piston pumps.

 

[Emile]

I second what Richard said, how is it when the vacuum is off the floor? That also could be a weak spot or kink in the hose. Under good suction it collapses internally, then starves and spools the pump, which then the hose opens up enough to start the flow and the cycle starts all over again. I've seen this many times with hydraulic systems, tight corners will erode a flap of inner material of the hose and starve piston pumps.

Yeah, I will try a different hose tomorrow What you guys said about the inner layer collapsing makes a lot of sense. I am not seing anything odd from the outside of the hose though, but as you mentioned it could be internally. Is there generally some material coating the inside of those hoses?

 

[Emile]

Maybe a clogged vacuum hose.

Do you have a lot of water behind the liner?

Do you think there is a relationship between having water behind the liner and any of my issues stated earlier ?

Thanks !
Emile

 

[Texas Splash]

It's a brand new pump, so I'm assuming drain plugs and o-ring are fine. I can try adding magic lube.

Brand new pumps do not come with lubed O-rings. You must apply some silicone pool lube to the lid O-ring gasket and perhaps the pump drain plug or-rings.

 

[duraleigh]

Pump running, have you looked to see if the skimmer is sucking any air?

 

[JamesW]

Do you think there is a relationship between having water behind the liner and any of my issues stated earlier ?

Thanks !
Emile

If you try to vacuum with water behind the liner, the vacuum head will stick to the liner because the liner is loose and floating.

Why is there so much water behind the liner?

 

[Emile]

Brand new pumps do not come with lubed O-rings. You must apply some silicone pool lube to the lid O-ring gasket and perhaps the pump drain plug or-rings.

I will deff lube the o-rings.

Pump running, have you looked to see if the skimmer is sucking any air?

No, there was no air coming into the skimmer.

If you try to vacuum with water behind the liner, the vacuum head will stick to the liner because the liner is loose and floating.

Why is there so much water behind the liner?

I don't know. I found the pool like this when I pulled the cover two weeks ago. It was fine last spring (2018). The liner is overdue for replacement and could have been leaking. I am getting it replaced in two weeks. I am a little worried that there could be another issue that made water accumulate behind the liner and that it would happen again with the new liner if left unsolved.

 

[JamesW]

You might want to contact a well or irrigation company to check the ground water level and devise a plan to control the ground water before you replace the liner.