Vacuum cleaner use results in loss of prime

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M

mrnamjama

Member
Jan 25, 2019
11
Australia
Hello folks

A couple of months ago I bought a Zodiac MX8 cleaner (powered by suction from skimmer, wanders randomly around the pool on tracks). When it is in use, the pool pump basket immediately starts filling up with air. This air also makes its way into the cardtridge filter housing.

As far as I can tell, the air bubbles originate below the check valve opening. I can see air bubbles rising up through the viewing window.

If I block the flow of water at the skimmer momentarily, there is an immediate effect at the pump in that lots of air appears in the basket. The skimmer is about ~16m away from the pump.

This problem existed before I got the MX8, when using just a standard brush/hose combination. It wasn't this bad. Without a cleaner attached, there is zero air coming into the pump basket, over the course of multiple days/weeks. The problem only occurs when suction is used to clean the pool.

I assume from all of the above that I have a hairline crack somewhere in the piping between the skimmer and the check valve. When there is a flow restriction on the intake, perhaps it opens up a little more and sucks air in. I am guessing. Any suggestions?

I am contemplating selling the MX8 and getting a robotic cleaner instead in order to avoid stressing the system to the point that I need to dig up piping.
 
m,

Welcome to TFP... A great place to find the answers to all of your "upside-down" pool questions... :shark:

I really doubt any of your pipes are cracked.. Possible of course, but highly unlikely.

When you run the vacuum, or your cleaner, the pump has to suck harder to move the water.. This exposes tiny openings that you don't really see when running from just the skimmer..

The most likely failure is with the pump lid O-Ring being damaged or not not lubed. The next thing is the O-Ring on the two pump drain plugs. Then the hose going to the skimmer from the cleaner. And any Jandy valve, including the check valve, that might be in the mix..

Depending on the size of your pump, it may not be able to suck enough water through just the cleaner hose.

I gave up on suction side cleaners at least 10 years ago... I have a robot and would never go back to a water powered cleaner.

Let's see if we can get some of our other members to chime in...

Thanks,

Jim R.
 
Getting a robot is the right thing. Suction cleaners that plug into a skimmer are often problematic. Everything has to be perfect in your system for them to work correctly.
 
Hmm interesting point on the pump not being able to suck enough water through the hose... let me make sure I understood that point correctly...

I inherited this pool and all its fittings through buying the house. Just recently I did a full audit of what's 'out there' and found that the pool pump is a single speed 1.25HP unit that is rated at 330 liters per minute (87 gallons per minute). The piping is rated at 162 lpm (43 gpm).

From what I've read, this seems like an overpowered pump, but it's not clear to me what side effects I can expect from it. Is the flow restriction when vacuuming starving the pump of the water it expects to be pumping?


Thank you all for your input so far!
 
Geday mrnamjama and welcome to the forum,

If you go ahead and put your pool details in your signature we can more accurately assess any problem.

Ive never been a fan of the suction side cleaners particularly when they are left in 24/7. The ones like your MX8 have a lot of moving parts adding to the complexity and increasing the back pressure on the suction side. As mentioned there are a lot of points from the skimmer through the auto control valve to the cleaner that can allow air in.

In normal operation the cleaner should be installed to prevent air getting in and the pump should have enough pressure to drive the cleaner and evacuate any air that does get in, out through the system. The MX8 auto control valve comes pre set to position 2, if you have a small pump set it to position 3 and for larger pumps set it to position 1. Check that all your connections are air tight, particularly the skimmer lid (many have a locking function), the auto control valve and the hoses. Run it with your pool water level a little on the high side, about 3/4 the way up the skimmer opening, at lest enough to ensure the auto control valve is covered.


 
mrnamjama said:
This is what I assumed at first, but I can replicate the symptoms at the pump by blocking water flow at the skimmer directly (with my hand, for example), without any hoses or fittings being connected
Click to expand...

This is not nessarsarily conlusive that you have a suction side leak in the system, by blocking the suction side you will increase the back pressure and force a lot of dissolved gasses out of solution and maybe allow a little air to be sucked in that wouldn’t under normal conditions.
 
mrnamjama said:
This is what I assumed at first, but I can replicate the symptoms at the pump by blocking water flow at the skimmer directly (with my hand, for example), without any hoses or fittings being connected
Click to expand...
I think you create a new, temporary suction leak when you do that ......blocking the intake at the skimmer introduces too much vacuum.

When you connect the vacuum and hose, you pull in air, correct? When you remove the vacuum and hose, you stop pulling in air, right? If I understand your description, that makes the hose/connections the culprit, I think.
 

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M,

Here is my experience with trying to use a vacuum line from years ago..

With the vacuum line installed, whenever I tried to turn the pump on, the pump basket would quickly fill with water and then air until the pump was no longer moving any water. I tried all kinds of things including buying a new vacuum hose. Nothing helped.

Then I used a Jandy valve that I could adjust between all vacuum hose input or all pool water input or anything in between.. If I started the pump using only the pool input, the pump worked find. I could then slowly move the Jandy valve until I had about 80% vacuum hose and 20% pool water and the vacuum worked. But, when I tried to adjust the valve to any more than 80% the pump would once again start sucking air.

The whole point being that I could not run with having only the vacuum line as the only input to the pump.

Thanks,

Jim R.
 
Jimrahbe said:
The whole point being that I could not run with having only the vacuum line as the only input to the pump.
Click to expand...

As far as I can tell, my pool only has one place where the pool pump sucks water from - and that is the skimmer box. This is where my vacuum hose attaches.

There are two other intakes near there, which are connected to the solar heating pump (two separate pumps, yes).

This all sounds very much like I ought to just get a robot cleaner and forget about these complications. Any recommendations?
 
M,

The best Dolphin Robot, without any bells or whistles, is the S200 from Marina Pool and Spa... Costs $700 bucks and free shipping.. You have to call, can't order on line.. The S300 and S300i have more options, but in my opinion not really needed by most pool owners and of course, cost a lot more.

Thanks,

Jim R.
 
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