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I haven't seen this on the forum, and it is weird. Pump pressure/suction is fine from skimmer (about 20psi) until we put the hose in to vac. The hose fills quickly with water, suction on the hose is good, then the pump pressure drops to zero. Have run water, small items, etc. through hose to see if it's clogged - all clear. Any ideas why the pressure drops to nothing when we try to vacuum? It only happens then - otherwise, pump pressure is good.
Inground concrete pool - 30k gallons.
Does the pressure on the gauge drop to zero or does the hose lose vacuum pressure?
The pressure on the gauge drops to zero. Interestingly, the hose gets heavy when the water pulls through it as it's first connected, but then the pressure drops and the hose no longer has any pressure holding it into the opening at the skimmer. It is still full of water, but the water isn't going anywhere. But what is really odd is that this doesnt happen when the hose isn't connected - the skimmer works just fine, and the pressure is normal.
In other applications, I've seen flexible tubing and hoses "delaminate" internally. Sometimes the bad section will appear normal on a low flow rate, like when you are using a garden hose to run water through a 1.5" flex hose, yet when you apply higher flow rates during suction, the bad section closes off most of the diameter of the hose.
Can you swap ends on your connections and check it that way? My guess is that it will act normal then. If it does, replace it.
Actually we tried inserted both ends into the skimmer and the result was the same. We also pushed the entire garden hose through the tubing (to see if we could push out anything that was stuck) with no difference. We ended up closing the pool yesterday and will try to figure it out when we open in the spring. Thanks for your suggestion!
Is it a convoluted hose? If so it may have cracked. Fill it with water and stretch it and look for leaks. I had a similar problem that only apeared when I started to vacuum and it pulled air through the split.
@handy1: It sounds like you are losing prime. It happens to me as well. All I have to do is re-prime and I am good to go.