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Inside and outside water - bug/feature?


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Replying to another thread I noted that if I used a water carrier outside with the external pump it seemed to use up water from the inside tank as well.

I proved this to myself over several water refills.

I checked (by ear) that only the external pump was running but the gauge for the internal tank still showed the water level going dow.

 

I was speculating that in some way the flow of water from the external tank was drawing water from the internal tank by a siphoning action overcoming the spring on the non return valve, but having trouble fully visualising this.

The non-return valve must be working in some fashion or the intrnal tank would fill up when the external pump was running.

 

I was just coming round to the view that this was not a bug but a useful feature.

Filling both internal and external tanks and using the external pump would use them both up without having to go outside half way through a shower.

The external pump also gives less flow but enough for a satisfying shower.

 

However it has just stopped doing this! :(

 

Next test is to have the internal pump switched on and the external pump plugged in and see what happens.

Will there be a stronger flow of water?

Probably not, but we shall see.

Hymer Nova 580 2016 and VW Touareg 2009 SE

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  • 2 weeks later...

Further investigation give some possible configurations:

[Noting that whatever the external rocker switch is set to the external pump always runs if it is plugged in.]

 

(1) Just use the outside connection to fill up the internal tank. Makes the snap connector into the water system pointless, but always uses the internal pump which is more powerful than the external pump. Reliable but can be fiddly as you are always topping up the internal tank.

 

(2) Just use the external tank. Pump isn't as powerful, and why have an internal tank?

 

(3) Use both tanks at the same time. External pipe plugged into the connector and electric plug connected. I haven't fully tested this yet so I'm not sure what the impact is of having two pumps of different pressures feeding the same system.

The best result would be that you get a higher overall pressure and flow and get a longer run time between refills as both tanks slowly empty.

Possible that the higher pressure from the internal pump may partially (or completely) close the non-return valve for the external pump resulting in the external pump running to keep pressure up but not delivering much (or any) water.

Main issue is that you could empty one tank and not notice because the other tank and pump is still supplying water.

This risks burning a pump out.

Lot of filling when both tanks are empty(ish).

 

(4) Use the internal pump to supply water, and at the same time run the external pump to fill the internal tank. This should give a longer run time between fills.

Advantage over (3) is that only the external pump is at risk but it still is at risk.

In theory works best with the external tank full and the internal tank perhaps 2/3 full.

Potential issues are that you could overfill the internal tank if you run the taps very slowly.

External pump could burn out without you noticing.I think (3) may be the best option but you do need to check regularly to make sure that neither tank is about to run out.

 

At the moment I am trying option (3) but thinking option (4) may be a better long term solution.

 

 

 

Hymer Nova 580 2016 and VW Touareg 2009 SE

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We have an older Nova 530 and if you want to fill the onboard tank from say an aqua roll you use the external pump to lift the water to the tank filler neck using the external switch. If on the other hand you want to use the aqua roll rather than the onboard tank you plug the external pump into the connection point and the tap micro switches control pump run, the external switch is turned off. We have a rocker switch on the seat base where the tank lives that selects which pump will operate, they don’t both run together. Dave 

Edited by wohnwagen
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  • I agree completely 1
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