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Posiflo pump problem?


Harvey

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Posted

2006 Autocruise Starblazer with a Posiflo pump.

 

After the pump has run, the water level in the transparent filter housing can be seen to drop and run back into the inlet pipe so that next time a tap is opened the pump is drawing in air, not water.

 

It seems from my research that there should be a valve inside the pump to prevent this so assume that if there is, it is faulty.

 

I do not know if there is a one way valve in the tank fitting either, which would prevent the backflow.

 

I am expecting to have to replace the pump with an equivalant Shurflo but before I do any knowlegable opinions / comment would be welcome.

 

Thanks,

 

Harvey

Posted

That you can actually see water in the transparent filter running back into the water hose indicates that there is an air leak between the pump and the water pick-up in the fresh-water tank.

 

It’s possible that the pump itself has an air-leak on its input side, but before replacing it, check that the filter is securely attached to the pump, that the filter is not cracked and that the water-hose leading to the filter is securely connected to the filter.

 

This type of pump does not have an integrated non-return valve as such, but the design of the pump’s internals should allow water to move through it in one direction only. It shouldn’t normally be necessary to have a supplementary non-return valve with this type of water pump, though fitting a valve may be useful if the pump has to ‘lift’ water from an external tank.

Posted

Harvey,

 

Our 2004 Auto Trail uses a Shurflo pump and has a non-return valve in the pipe leading from the tank just before the inlet filter you mention. It is quite a large (3" - 4" long) quick fit ended device with an arrow showing direction of flow.

 

Keith.

Posted

*Fixed*

 

I am sure you would like to know how ...

 

Thanks both, especially Derek.

 

I have established that I definitely do not have a non-return valve in the feed line or in the fitting at the tank.

 

As Derek has stated that there is not one in the pump either :--

 

I had already checked the filter for visible cracks or damage and that all the connections were good as far as I could tell.

 

I have tinitus, so my hearing is slightly impaired but I got my ear very close to the pump and filter and could just discern a slight noise: air being sucked in?

 

I removed and cleaned the filter. renewed the PTFE tape on the screw fittings and put a light smear of silicon grease on the 'O' ring on the removable part of the filter and all back together. Fixed? No.

 

So, either a new filter then, or a new pump and filter.

 

While giving the pump a good staring at and with nothing else to do, I thought that I would just 'nip up' the six screws holding the top part of the pump to the lower body. They took quite a bit of 'nipping' and that was the fix. There must have been air leaking past the gasket / seal between the two parts of the pump.

 

I knew I would get useful help here and that has saved me about £60 for a new pump. :-D

 

Oh, and now when the tap is turned off the pump cycles for a much shorter time before it shuts off.

 

Harvey

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