Booster pump creates hammer - Help please

Good Morning all you Wrenches!

I have a bad water hammer each time my booster pump comes on under my house. The older jet pump/80 gal pressure tank were removed and replaced with a Grundfos MQ and that is when the hammer started. Here is my setup:
1HP submersible well pump (water level ~250') filling storage tank
1.5 HP Grundfos MQ-45 booster pump for house pressure

I have several small hammer arrestors that were installed during a remodel but never had a hammer prob with the old pump/pressure tank. Now that I do have hammer with the MQ, they aren't working. I know some of you don't like the MQ, but obviously I didn't do my research before buying it
I was thinking of a CSV, but have read it won't work with the MQ.

Anyway, I am wondering what kind of sage advice you might have on my problem. Thanks!!

Matt

You added a 1.5 horsepower booster pump to move water within the house when a 1 hp was sufficient to bring the water volume up from 250 feet? That seems pretty powerful to me, but I am only an observer. Why would adding more pumping power eliminate the need for a pressure tank? It just feels odd to this non-pro.

I could maybe see that the booster pump might not need an additional pressure tank, but I can't see how it is going to remove the need for the pressure tank for the output of the submersible. I am pretty sure this is a typo in https://grundfosmq.com/

Aside from pump, an MQ unit is complete with motor, diaphragm tank, pressure and flow sensor, controller, and check valve. The controller ensures that pump starts automatically when consumption ceases.

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ffmedic said:

80 gal pressure tank was removed

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“Re-installing” a pressure tank might solve the water hammer. The opening to the pressure tank needs to be installed straight in line from the pump. Then the water can tee off to the side before the pressure tank, going to the house. That way when the pump starts, the surge of water goes straight into the pressure tank. The tank should absorb most of the surge and make it hard for any of the transient pressure wave to tee off at a 90 degree angle.

ffmedic said:

I was thinking of a CSV, but have read it won't work with the MQ.

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No the CSV will not work with the MQ. The MQ has a built in pressure switch and pressure tank about the size of a baseball. You can’t get a CSV installed between the pressure tank/pressure switch and the pump, so it won’t work.

Reach4 said:

You added a 1.5 horsepower booster pump to move water within the house when a 1 hp was sufficient to bring the water volume up from 250 feet? That seems pretty powerful to me, but I am only an observer. Why would adding more pumping power eliminate the need for a pressure tank? It just feels odd to this non-pro.

I could maybe see that the booster pump might not need an additional pressure tank, but I can't see how it is going to remove the need for the pressure tank for the output of the submersible. I am pretty sure this is a typo in https://grundfosmq.com/

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It is common to have a small well pump to slowly fill a storage or cistern tank, because a small amount of water is all the well will produce. But once you have the storage or cistern tank filled, you can use as large a booster pump as you need to pump as much volume as you want into the house.



You would not be having problems with a CSV system. This is why I look for more pump companies to build controls into their pumps, which prevents the installation of a CSV. Making sure pumps don’t last too long just makes sense, I mean dollars.

Thanks valveman! Makes sense. Glad I still have the big pressure tank. I'll give it a go.
Crazy thing is, I bought a CSV years ago, when I was thinking of running the sub pump straight to the house to limit wear on it. It's a 30 yr old pump and about 10 years ago, I added the storage tank and booster. I know when it goes, I will get an inferior pump. The CSV never got installed and I think I got rid of it!
Thats why I fight fires and leave the plumbing to pros!

Matt