Low Suction, Normal Return flow

  • Last Post 15 May 2019
JHP1958 posted this 05 May 2019

My gf had a salt 30' foot round when we met. I found the supply was barely filling the pump basket and if you put a skimmer plate and hose in it bare has suction and the clear pump lid shows water about 1/3 down. At the same time the return is strong. I replaced the pump with the 1.5 hp Pentair Dynamo that is recommended and was on there originally. I also replaced all the PVC and valves with new. Still have  a weak supply side and strong return. None of this makes any sense to me.

I have an inground with a Hayward superpump and 4 returns, so this is all new to me, but there is something wrong here on this above ground. 

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InyoRob posted this 06 May 2019

We'd be glad to assist you. This sounds like an odd situation. Is the water level at least halfway up the skimmer door opening? Is the equipment close to the pool? What is the PSI reading on the filter gauge?

JHP1958 posted this 11 May 2019

 Thanks for your help.  I'm sorry it took so long to get this information to you. 

Yes, the water is more than halfway up the skimmer door opening. The pressure is 14. There is no leaking around the pump reservoir cap when it's turned off. I thought maybe the seal wasn't tight enough, though that doesn't seem to be the case. Also, the water floods the pump when it's off and the cap is off the reservoir, so there is no obstruction of any kind in the line, there is a free flow of water. 


InyoRob posted this 13 May 2019

What kind of filter do you have?

JHP1958 posted this 13 May 2019

I'm at work at the moment,  but it's a Pentair that holds 200 lb of sand I believe.  I just changed the sand last year. 

InyoRob posted this 13 May 2019

If you put the filter valve in the recirculate position and run the pump, does the system work properly?

JHP1958 posted this 15 May 2019

It works properly in recirculate without anything in the skimmer. I haven't yet tried it in recirculate with a skimmer plate, hose and vacuum head. That of course is not normally done. 


InyoRob posted this 15 May 2019

The fact that it works on recirculate would lead me to believe that it is something in the filter. Either it needs to be backwashed or treated with a Sand Aid product. You mentioned that the sand was changed. Did you use #20 silica sand (.4-.5mm)? The wrong sand could cause issues.

Check out our video below for reasons why the pump may lose prime when the vac plate and hose are used to vacuum the pool.

JHP1958 posted this 15 May 2019

Yes, the sand is silica sand from the pool store.  I will check the O-ring and lube it with silicone as well.

InyoRob posted this 15 May 2019

Good luck. Let us know how this gets resolved.