March Pump Trouble

I'm having trouble with my march pump. It doesn't like to pump boiling water very well. Otherwise, it works just fine. When trying to pump boiling water, it starts out with a good flow and then once the pump head heats up it drops to a trickle. Has anyone else experienced this problem? The pump is advertised as capable of handling boiling water and the pump head is rated to 250F. It should pump right? Is there a problem with my pump head maybe? I'm only trying to pump the water up about 3 feet.

Any help would be great

It is probably cavitating in the pump head. The pump is rated to work with liquid at that temperature, but not with a bunch of air bubbles in it.

I had that problem with mine when trying to pump out of a kettle with a dip tube. After I removed the dip tube, I had no more problems.

Right, because it is bubbling right up into the dip tube causing a break in the siphon and cavitation in the pump head.

You can't pump boiling water or wort with our common March or LG pumps. The liquid will cavitate and the pump willl lose prime. You can, however, ususally pump liquids at about 200*F. It only takes the hot liquid a few minutes to cool off enough to pump it if you get it too hot. The temperature ratings are related to the strength of the pump head in a pressurized system and have little relevence to the way we use them at very low head pressures.

Interesting.....I thought about maybe gas bubbles forming from the boiling water but, since I have a center inlet pump and I keep the outlet pointing strait up, I thought that any water vapor would be channeled up and out of the pump and wouldn't really hurt anything. Looks like it's more of a problem than I thought. Did a quick google search and found some reading on cavitation. Good stuff. Guess I'll have to make some temperature adjustments to my process.

Thanks for the info guys

Catt22 said:

You can't pump boiling water or wort with our common March or LG pumps. The liquid will cavitate and the pump willl lose prime. You can, however, ususally pump liquids at about 200*F. It only takes the hot liquid a few minutes to cool off enough to pump it if you get it too hot. The temperature ratings are related to the strength of the pump head in a pressurized system and have little relevence to the way we use them at very low head pressures.

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I've been pumping boiling water just fine after I removed the dip tube from my kettle - I wonder if the reason may be because I have more flow restriction on the outlet of my pump than on the inlet - I use camlock disconnects on both, but have the 1/2 inch street elbow with threaded camlock on the input and the barbed (smaller ID) camlock on the output.

Im sure you guys already checked this but... Is your diptube "swagelock" fitting tight and leak free? If your pump begins cavitating after the wort hits the bulkhead / top of your diptube then you are likely drawing air into the intake and losing prime... Boiling liquid does not create bubbles in the pump. JJ

I've been pumping boiling wort through my plate chiller and back to the BK for sanitation purposes without any trouble at all. I've got a SS dip tube connected with a Parker compression fitting.

I recirculate boiling wort to sanitize my plate chiller with a 809HD and have had no problems with priming or cavitation.

MotleyBrue said:

Im sure you guys already checked this but... Is your diptube "swagelock" fitting tight and leak free? If your pump begins cavitating after the wort hits the bulkhead / top of your diptube then you are likely drawing air into the intake and losing prime... Boiling liquid does not create bubbles in the pump. JJ

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It is not creating bubbles in the pump, it is creating bubbles in the dip tube. The boiling causes bubbles to form, some of which are in or around the dip tube, that are then drawn in. Get enough bubbles to form and then will create a loss of siphon.

I can lower my temp just a hair below boiling and have no problems. If I try to pump rapidly boiling liquid I will sometimes lose siphon. I seriously doubt it is because there is a leak in the fitting.

Now, in my case my dip tube IS part of the problem because all I did was take a street elbow and turn it 90 degrees so it's facing straight down to the bottom of the kettle, against the rim. When the liquid boils, the bubbles rise straight up into the dip tube. But it was a very cheap and easy alternative to making a custom copper or stainless steel diptube with compression fittings and all that, and it works great except I have to be careful about trying to pump rapidly boiling liquids with it.