Grundfos SCALA 2 booster pump

[Tamarack]

I recently replaced an old booster pump and pressure tank with a Grundfos SCALA 2 continuous pressure booster pump (which has a built-in pressure tank). The pump pulls water from a cistern which is less than 10ft below the elevation of the pump. However, we are consistently having pulsating pressure (good pressure for a minute then very low pressure for another minute), also there seems to be a lot of air in the line as well. The pump seems like it's having a difficult time priming and I'm unsure if there is air somewhere in the line between the cistern and the pump.

There does not seem like there is any leak in the house and there is a check valve in the supply out of the pump to the house so I'm guessing no water/air would be able to get back into the pump.

Any ideas? Thank you!

 

[Valveman]

The check valve needs to be on the suction side of the pump, not the side going to the house. That could be causing your problem. However, those variable speed kinds of pumps are made to sell and be easy to install, not to work well or last very long. The Scala was supposed to replace the MQ. But they haven't retired the MQ as the Scala isn't holding up well in the real world. If you want something that will last 30 years, deliver strong constant pressure, and never have to worry about it use a Cycle Stop Valve or the PK1A kit as needed to control a J10S pump. The old J10S pump hasn't changed in my lifetime, and using a CSV to stop the cycling and control the pump will make it last even longer. It would look something like this.

 

[Tamarack]

J10S pump

Thank you Valveman! It freezes where I live so our pump is in the basement and sucks water from the below-grade cistern from a foot valve in the cistern. I double checked and the check valve is on the suction side of the pump where it pulls water from the cistern. So the low pressure problem must be coming from something else. Also, the pump constantly shows an error message that there is no water when there is, which leads me to believe there might be air in the line between the cistern and the pump.

A pump technician came out and said that the line from the house to the cistern may have an air bubble trapped and suggested adding a standpipe before the water enters the pump that I would fill to help prime, but that doesn't seem to have made a difference.

I like the CSV and pump you suggest and wish I had seen that before I purchased my system. My friend who recommended the SCALA 2 had one at his place and really like it, however, he just told me the other day that he had to replace his after 5 years (started to leak)...next time I'm checking this forum first!

Do you think if I added the CSV I could still use my SCALA until it dies and then replace it with that J10S? Or do I need to just replace the whole thing? Thanks again for your recommendations!

 

[Valveman]

Either you have too much restriction in the suction pipe, a leak in the suction pipe, or the pump is just not good. Your friend must have a very lightly used water system for the Scala to last 5 years. Most barely make it past the warranty date, which is planned and just the way things are built these days.

If your Scala was pumping good water and just not shutting off as it should or something, we could add a CSV and make it work like a normal pump. But if it won't make water, you are going to need to do something. You can keep messing with the Scala or get a regular jet pump controlled with a PK1A and not have to think about your water system for 30 years. It is rare to ever hear back from a CSV customer as water just keeps coming out of their faucets when opened. They go on with their lives, never having to worry about the water system, which is how it should be.