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Water flow issue with external pump


rjnd
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I have just recently changed caravan to a 2014 compass Rallye 634. On first outing we had a issue when using the external aquaroll. When we open the tap using the external water source no water is produced for approximately 20 seconds. Then the pump switch will light up, water will flow for about 20seconds,  then die and stop for 20 seconds then start again and so it goes on

This van has a internal tank also and we had a minor issue with this. We used this as our source due to the aquaroll being unusable but the pump ran permanently so we had to keep switching it off. Anyway it went back to the dealer who sorted the internal pump issue, adjustment of pump only needed but the dealer is adamant that the starting/ stopping of the external pump is completely normal for a modern van and that I should stick to the internal source. 
I cannot believe that this is normal as it basically renders the external source useless. My old van would produce water as soon as the tap was opened and keep running until you closed it. 

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Already been done twice. Has made no difference. Really trying to find out if anyone with an onboard tank has the same problem. Dealer claims it’s normal function !

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It really does sound like a pressure switch adjustment issue.  When you open a tap the reduction of pressure in the system is sensed and power is sent to the pump. The pump operates to try and get the pressure back up, but as the tap is open water flows from it. When you shut the tap, pressure builds in the system and is sensed and the power to the pump is switched off. 

In the case of your van it seems the sensor is detecting that the switch off pressure has been reached, even though the tap is open and so it cuts of the electricity to the pump. That then leads to the pressure in the system dropping because the tap is open and the cycle repeats. The only way to stop it is to adjust the pressure sensor to a point where the pump runs consistently and only shuts off when the tap is closed.

I've got nothing to do on this hot afternoon

but to settle down and write you a line.

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It could be that the one-way valve is either missing or leaking and allowing water back into the barrel so the pump keeps starting up to rebuild the pressure.

2018 Passat B8 Estate 150GT TDi150 towing a 2018 Bailey Unicorn S4 Seville

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Sorry really trying to find out if this is normal or not. Not really looking for solutions just want to know if the dealer is right or wrong 

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Absolutely not. We have an internal tank and external and if using the aquaroll the whale pump operates normally simply giving us continuous water flow. Dealer surely isn't right here?

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Just reread the OP. 

 

What is odd is the wait for the pump to initially switch on. It should be almost instantaneous when a tap is opened.

 

Presumably we're talking of a single internal pump in this case and it draws water from both internal and external tanks, with a valve to switch between the two sources. In other words the majority of the system is exactly the same for either source, it's the piping from the diverter valve to the two tanks that is different. 

 

So why should it take 20 seconds for the pump to operate when using one tank when the same pump reacts  instantaneously when switched to the other?

 

IIRC the hose to the Aquaroll is 'dumb' with just a filter on the end, so there's nothing that could cause an issue. Logic therefore suggests there's a problem with the plug/socket for that hose as it's the only 'difference' left. I know from bitter experience that they can be troublesome and sometimes the problems are illogical. I once replaced all the valve bits and 'O' rings in one, but a problem persisted. It turned out that a tiny bit of plastic had broken off internally and messed up the water flow. A replacement socket sorted the issue.  

I've got nothing to do on this hot afternoon

but to settle down and write you a line.

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1 hour ago, Steamdrivenandy said:

Presumably we're talking of a single internal pump in this case and it draws water from both internal and external tanks, with a valve to switch between the two sources.

 

Except that the OP states:

"Anyway it went back to the dealer who sorted the internal pump issue, adjustment of pump only needed but the dealer is adamant that the starting/ stopping of the external pump is completely normal for a modern van and that I should stick to the internal source. "

I think it would help if the OP could more accurately describe the exact makeup of his water system i.e. what pumps, switchable and non-return valves are incorporated and where. We may then have a better chance of determining what might be going on.

Life is not a rehearsal . . .:)

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1 hour ago, KnausCol said:

 

Except that the OP states:

"Anyway it went back to the dealer who sorted the internal pump issue, adjustment of pump only needed but the dealer is adamant that the starting/ stopping of the external pump is completely normal for a modern van and that I should stick to the internal source. "

I think it would help if the OP could more accurately describe the exact makeup of his water system i.e. what pumps, switchable and non-return valves are incorporated and where. We may then have a better chance of determining what might be going on.

My understanding is that it’s a whale system which has  settings of EXT- O and INT on the control panel  You switch to External which fills the onboard tank from the aquaroll which incidentally seems to fill just the way the taps operate when on aquaroll use.

 once the onboard is full the pump stops and you then have the choice of switching to internal to use the onboard or switching to “O” to use the aquaroll  Also as you use the onboard tank you need to switch to EXT periodically to replenish the tank from the aquaroll as it doesn’t auto fill. I simply can’t see how it could possibly be designed to operate the aquaroll as it does as this would mean if the internal tank pump failed we would have no proper useable water source

 

Sorry messed that up. Read the quote please 

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Reading the OP's comments I can see that we're talking some type of electronic diverter system here, not a manual diverter valve. What's still not clear to me is whether the system is using just one onboard pump or has two pumps, one for the onboard tank and one pushing water in from inside the Aquaroll?

 

If it's just one pump then it should operate the same, whichever of the two sources are used.

 

If there are two pumps and the internal one is working fine, then the issue is likely to be the adjustment of the pressure sensor associated with that external pump.

 

One theory I've thought of  that theoretically might be causing the problems is if the two systems share a pressure sensor and each system reacts differently to the conditions in the water system. Then you'd have to set the pressure sensor to a compromise position, possibly so that one or other system worked fine but the other didn't, or that both systems worked sub optimally. The dealer's insistence on the internal tank being used may be an indication that they've chosen the former option in adjusting the sensor.   

I've got nothing to do on this hot afternoon

but to settle down and write you a line.

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