One of the things I’ve had problems with recents has been my March Pump. It’s the 809HS model and it’ll get some cavitation issues, especially when pumping hot wort. This is a common problem, and one of the the reasons I most hear for this issue is that the impeller in the 809 is really short. Well deciding that mine needed a cleaning anyway I popped it open and sure enough the impeller looked tiny – the blades had a significant gap between their end and the edge of the interior of the pump. Recently I saw that Williams Brewing was selling the impeller that is used in the March 815 pump, but also fits fine in the 809. Since the 815 uses a much larger impeller I figured this could work out well so I ordered one.
The first picture is of the standard impeller that came in my March 809HS. You can see how far away the blades are from the wall of the pumps interior and it’s not hard to imagine why with hot liquids you could see some significant cavitation issues. I’m really surprised that anyone would bother to create a pump like this when it would seem a trivial expense to include a larger impeller. Perhaps it was a market decision so they could have various sizes of pumps? Or maybe there was an initial engineering reason. Either way I’m really glad I decided to replace it.
So this second picture is of the March 815 pump installed in my pumps housing. You can see the impeller blades are much longer leaving only a small gap between the end of the blade and the wall of the housing.
Taking the pump apart to get to this is just 8 screws. The one thing to watch out for is the narrow o-ring. When putting it back together you need to make sure that it’s not twisted or you won’t get a good seal and the pump won’t work. Also you run the risk of ripping the o-ring and then you’re really out of luck short of replacing it with a newer one.
So far I haven’t done a brew day with the new impeller installed (that will come this weekend). However I ran both a hot PBW solution through it, and a StarSan solution through it to not only test for leaks in the pump, but also to see just what this larger impeller could do. When I first started to pump through it I was shocked by the flow rate. Not having a flow meter handy I simply timed how long it took to run the cleaner our of one bucket and in to another. It took just over 1.5 minutes to run the 5 gallons of cleaner from one bucket to the other. That’s close to 2.5x better than I had seen with the old impeller. I also didn’t have any cavitation issues – though the PBW was only around 140 degrees as opposed to the near boiling temperatures I run through it on a brew day. Still I’m really optimistic and excited to see how it performs.