pump slowly losing prime

[sjpoolowner]

mas985, would you consider above picture fully primed? Or should I really not see any air pockets?

I haven't really noticed the filter pressure change. It is about time to clean up the filter (a cartridge filter) though.

I assume "reducing the suction on the pump" is bad for priming as I think I should go full force when priming? So that's why I was able to achieve better priming when only the main drain was open? BTW, I don't have any valve to control the water flow. I can only either shut off the skimmer using the plastic thing under the skimmer basket or open both main and the skimmer.

I'll add some more water just in case.

So 2000 rpm sounds too low?

Thanks again.

[mas985]

A full primed pump will not have any air left in the pump basket but at lower flow rates it will take more time for the air to purge. I have a 1/2 HP pump and the flow rate is around 65 GPM. It will take sometimes 5 minutes for all the air to leave the pump basket but it eventually will. However, with a VS at full speed, it shouldn't take more than a couple of minutes for all the air to be purged.

I assume "reducing the suction on the pump" is bad for priming as I think I should go full force when priming? So that's why I was able to achieve better priming when only the main drain was open? BTW, I don't have any valve to control the water flow. I can only either shut off the skimmer using the plastic thing under the skimmer basket or open both main and the skimmer.

What I mean by reduced suction is not reduced flow rate but reduced suction head loss as measured by "in-hg". Having the main drain and skimmer fully open reduces the suction head loss which in turn increases the flow rate so the pump should prime faster. But having higher suction head loss, will increase the suction at the pump basket (i.e. lower pressure) which in turn can draw in more air.

[sjpoolowner]

Thank you again. I did a little experiment and tried to block skimmer side flow using the thing and ran the pump at 3000rpm. Then to my surprise I actually noticed water flowing into the skimmer pipe. I examined the plastic thing (what is it called?) after turning off the pump and found that the flap that I initially closed the hole was actually moved. I guess it does that when the pump is running really fast and main drain only can't provide enough flow? So it looks like when I primed the pump, I actually opened both the skimmer and the main drain.

So assuming that no air is sucked into the skimmer, what are my options now? Try to run the pump at full speed regularly? Replace the o-ring? Add lube to the pump lid area?

Would appreciate any help. This issue is really bugging me now.

[mas985]

So I take it that even running at 3000 RPM did not remove all the air?

I removed the plastic flaps from my skimmer a long time ago. For efficiency reasons, you really don't want to restrict flow in anyway and leave everything wide open. Plus restrictions on the suction side can cause air leaks as well as other issues.

But besides the pump lid, there are several other areas where air can get sucked into the plumbing; pump drain plugs, valves, and worst case, a cracked pipe. Any construction over the buried pipes recently? One trick to find leaks in plumbing is to spray shaving cream on the various valve/plug connections and see if anything gets sucked in. If you eliminate everthing on the pad, then look again because a lot of times you may think there is no leak when in fact there is. Hopefully it isn't in underground. Air leaks can be one of the hardest things to find. Water leaks not so hard.

[sjpoolowner]

Yes. What you see in the pic was as best as I could do at that moment. I might have done better if I keep repeating it. Unless I did something wrong.

What I did to prime was: stop the pump, open the air valve of the filter, run the pump at high speed (up to 3000 rpm) until water coming out of the filter air valve, close the filter valve and wait a little. I didn't open the lid since there was water in the basket except for one time to clean up the o-ring and lid surfaces. And I had to try this sequence multiple times to achieve that.

Anything to try for the lid?

I'll try the shaving cream method. I do hope it isn't in underground!

Thanks a lot.

[BigDave]

sj,
Did you happen to notice if your returns had strong flow when you were running the pump at high speed after it was primed?

[mas985]

Besides Bigdaves question above, what was the filter pressure at 3000 RPM after priming?

Also, it is somewhat counter productive to open the filter bleeder valve when the pump is off since this allows air into the filter which then displaces the water actually making it harder to prime. You are much better off opening the valve only after the pump is turned on to prevent draining of the filter.

Silicone pool lube is the best stuff to use on the pump lid and drain plugs.