Does a new water pump need priming?

[Capt. Rodbone]

We recently moved our new to us grand Banks 42 to a temporary home in a marina reasonably close to our house. On the five day trip, we had a water pump issue (sinks/heads/ etc not engine). I had a new one installed upon arrival. This morning we noticed when we turned on the master panel switch for the aft cabin head the pump continued to run. I went and checked the water tanks and both tanks were empty. I filled each tank to approximately 60% capacity however the pump seems to continue trying to pump. I can ask the installer tomorrow however I’m wondering if a water pump has to be primed? It’s possible they put it in and didn’t even do that I suppose.
As always any replies and thoughts are very much appreciated!

 

[psneeld]

Did you open all the faucets and showers (not necessarily all at once) to get the air out of the system?

 

[RCook]

Is the valve at the outlet of the tank open?

 

[Capt. Rodbone]

Thank you. I had not but I just did. Here is what I experienced. Galley sink good water pressure and no air shooting through. Same thing with forward cabin sink and the head seemed to work fine. Did not turn the shower on. The sink and shower in the aft cabin were fine regarding water flow and no air pockets.

What is interesting and probably significant is the aft head is the one that seems to make the pump continue running. The forward head is working fine. Maybe it is not a pump issue but something related to the aft head.

 

[Capt. Rodbone]

If you mean to the water tanks yes. Water is flowing fine and consistently to all faucets and showers. If you possibly mean to the wasteholding tank I’ll have to go down and look however I have not turned one off and it has worked fine and we did a pump out upon arrival at this marina.

 

[Gordon495]

I think what you experiencing is the drop in pressure to push the water further down the line. It takes more pressure and your bladder drops quicker and makes it pump a little more. That water pump is keeping your buffer tank pressurized. The tap closet to the buffer tank will probably take less pressure and cycle the pump least often.

 

[Capt. Rodbone]

First let me say how much I appreciate this forum and all of the thoughtful and quick responses so many of you share.
I realized during the middle of the night that my issue after checking a few things suggested here wasn’t likely my water pump but more likely the line from the aft head to the holding tank. After watching a video on YouTube and repeatedly going through the steps suggested the line cleared and all was well. I tested it multiple times just to make sure but it was a clogged line between the head and the holding tank. The pump I heard running wasn’t the water tank of course, but the pump moving Black water to the holding tank. I’m sure to the majority of you folks this is 101 level things however none of you have been condescending with your replies.
Thank you again!

 

[hmason]

What’s really great about your situation is that you persevered and fixed it yourself. One merit badge for you.

 

[BruceK]

Captain Rodbone, that is how we owners learn about boat operating systems,especially those prone to give trouble,by tracing and fixing things going wrong.

 

[pjtemplin]

Thinking higher level, it depends on the type of pump. A positive displacement pump (think impeller type) will pump "anything", air or water; no need to prime it. A centrifugal pump (think spinning wheel with vanes) will only pump liquid, so you either need to prime it or you need to let gravity do its magic.


(Random factoid: fire engines use centrifugal pumps to be able to hit 1500 gpm or more, but for the times when they want to suck water from swimming pools or similar, they have a small electric positive displacement priming pump to evacuate the air. The centrifugal pump is driven by a transfer case behind the transmission; it literally diverts the full engine horsepower to the pump and renders it unable to drive under its own power (usually). >350HP is required to achieve >1500gpm, and that priming pump is quite noisy when used.)

 

[Flatswing]

Cptn. Rodbone: well done. Do you have Vacuflush heads? The pump you hear is probably the vacuum generator. Any little bit of crud in the (4) duckbills in the generator pump or under the bowl seal causes it to keep running. Consider getting acquainted with Peggie Hall’s treatise “vacuflush 101”. Then you’ll be an expert in no time