Water system layout

[paulweller84]

Hi all, I'm hoping this is the best place to ask this question...

I recently sold my Bailey UN3 Cartagena and have bought a van to convert into a camper. As we've had caravans for years I want to set it up like my old caravans with regard to the water system i.e. have an aquaroll and submersible Whale pump/socket.

Despite spending a considerable amount of time with my head under various caravan sofas sorting out issues with water systems, now I need to build a water system from memory I'm finding it hard to recall what is needed. I have tried Googling water system diagrams but struggling to find anything that doesn't have an inboard water tank or internal pressure pump.

Can anyone point me in the direction of a diagram or even a photo of the internal layout of the water system on a caravan that uses an external Whale submersible pump and non-microswitch taps. Many thanks in advance to anyone who might be able to help!

Paul

 

[Jcloughie]

Welcome to the forum Paul.

I found a few, but this link. seemed helpful and included this.




John

 

[paulweller84]

Thanks John,

This is basically what I was thinking, but every diagram I looked at had internal pumps or tanks, and in my head I was thinking surely just a submersible pump and an accumulator would do the job!

 

[ProfJohnL]

Jcloughies link is pretty comprehensive, but if you are only looking for cold water then you can omit the accumulator and water heater from the picture.

Bearing in mind the limited space in most van conversions and for simplicity the Whale system with the pressure switch incorporated into the pump connection on the side of the van/caravan

is hard to beat.

 

[paulweller84]

if you are only looking for cold water

Having experienced the luxury of nice caravans, we're opting for a Truma Combi 2E system. Love our creature comforts.

The plan was to have a cold-only system for use when not on campsites, fed from a separate 10L container under the sink, but sharing a tap (isolation valves on the inside and outside feeds could be open/closed to control where the water comes from). The issue is, these simple campervan kits you can get use microswitch taps, so it seems my only option is to change my main hot/cold/aquaroll system to a microswitch type, or have two taps on the worktop. Don't love either idea to be honest.

 

[ProfJohnL]

You don't need to use the microswitches. Many taps are supplied with the microswitches as a convenience. The tap itself should perform perfectly well on a pressure switched system

 

[paulweller84]

You don't need to use the microswitches. Many taps are supplied with the microswitches as a convenience. The tap itself should perform perfectly well on a pressure switched system

Ah, hadn't though of that but it seems obvious now - even a microswitched tap is still essentially just a tap.

The only difficulty there is we want a tap that has a pull-out shower head (in the campervan, the kitchen and bathroom are the same room! ) - and all the combined taps we can find with microswitches are ugly looking things!

 

[JTQ]

The circuit in John's post #2 will not work in the case of most as purchased submersible pumps than will pass through the port in an Aquaroll.

The logic is these pumps will be, to achieve that slimness, rotodynamic centrifugal pumps not displacement, thus the water can back flow so not hold the pressure on the switch, when the switch attempts to stop it.
There has to be an additional non return valve placed somewhere between the water inlet to the pump, and the pressure switch.
Ideally, this should be after the pump as there the pump's pressure better opens the non return valve, and it does not inhibit the challenges its location before the pump presents to filling that.

 

[JTQ]

The selection of typical submersible pumps, in combination with "pull out shower heads" is not a particularly wise combination where basic products are used.

These rotodynamic centrifugal pumps' flow modulates with the "head" [pressure] they are asked to develop; this characteristic means that as the hight the shower user holds the head, the pumps flow will change.
The knock on from that with a split hot feed the achieved temperature at the shower head changes as the hight of the head changes. A shower modulating from hot to cold and back is far from ideal.
If the head is fixed then this issue does no arise.
This can be addressed by altering the pump type and/or introducing temperature regulation.

 

[paulweller84]

The selection of typical submersible pumps, in combination with "pull out shower heads" is not a particularly wise combination where basic products are used.

These rotodynamic centrifugal pumps' flow modulates with the "head" [pressure] they are asked to develop; this characteristic means that as the hight the shower user holds the head, the pumps flow will change.
The knock on from that with a split hot feed the achieved temperature at the shower head changes as the hight of the head changes. A shower modulating from hot to cold and back is far from ideal.
If the head is fixed then this issue does no arise.
This can be addressed by altering the pump type and/or introducing temperature regulation.

What's the difference between a pull-out shower tap and the usual mixer shower with a hose you'd have in a caravan? Before turning the tap (shower) on, the hose would be pulled right out and the shower head fixed into a mount at head height, so not sure what the difference is? Unless I'm missing something.

 

[JTQ]

What's the difference between a pull-out shower tap and the usual mixer shower with a hose you'd have in a caravan?

Nothing, that is what I covered with : "If the head is fixed then this issue does no arise."

Any shower head you can move its hight during the shower will exhibit this characteristic, if using the pump set up discussed.

 

[paulweller84]

Nothing, that is what I covered with : "If the head is fixed then this issue does no arise."

Any shower head you can move its hight during the shower will exhibit this characteristic, if using the pump set up discussed.

Got it, as I suspected - I was missing something. 🤦‍♂️

Thanks for the info

 

[ProfJohnL]

Certainly the separate whale pressure switch seen on the left:-

has a Non Return Valve built into it. I guess the inlet on the right will also have one as its essential for a pressurised system to work.

It does not need an additional NRV between the pump and the inlet housing in the side of the van.

As you intend to have hot water, then the addition of a surge damper (the up turned bottle) on the cold system should smooth out the flow of both hot and cold water to the shower mixer to help maintain steady water temperature when having a shower.

 

[paulweller84]

This is where I've got to now...

High flow Whale submersible pump connected to Whale socket with Intelligent Control (which eliminates the need for a surge damper). T-piece splitting hot and cold side with a NRV and drain down valve before the combi boiler. Have I missed anything here?

The off-grid side I've decided to run a separate, small microswitch tap on the other side of the sink connected to the 10L container.

 

[JTQ]

As said it is essential for the pressure switch based system to work that there is a non return valve somewhere between the pump's inlet and the pressure switch. For the pump type being discussed.

The circuit in post #2 does not include this essential item.

If the Prof's statement is right, that essential non return valve has been included in the unit along with the pressure switch.
Whatever way that is provided, for a pressure switch based system to function correctly, one has to exist.

 

[ProfJohnL]

Based on what you have described, you will definitely benefit from having the Surge Damper/Pressure accumulator included as shown below

Here's the reason why it helps:-

Most water heaters in caravans are storage heaters, and they use the cold water being pushed in at the bottom to expel the heated water which accumulates at the top of the tank. The cold water enters through a non return valve which stops the tanks content and pressure from back flowing and emptying through the cold water pipes. The tan is deliberately designed to leave an air cap at the top above the hot outlet pipe. This is necessary to accommodate the expansion of water as its heated.

Initially when you prepare the system you have to fill the heaters tank, by opening a hot tap and allowing the pressure of the cold water to fill the tank.
The cold water flows in and displaces the air in the tank. you know when the tank is full becasue you get a steady flow of water through the hot tap, when you close the tap, it stops the outflow, but the pump will continue to push water in raising the pressure inside the tank and in the cold pipework equally until it reaches the cut off pressure set on the pressure switch .

The cold feed and the cold water in the tank are at the same pressure. When the heater is turned on, as the water temperature rises, it expands, but becasue of the non return valve on the heater input and the closed taps all the expansion has to be accommodated by the air cap in the tank, Consequently the air cap is squeezed and its pressure rises above the water pressure in the cold pipework which is still above the pressure switches threshold.

Once the water is hot, the pressure in the hot side is greater than the cold, so if you open a mixer tap (e.g shower ) the pressure in the hot tank will cause the hot to flow, and it will add some of that pressure to the cold side(through the mixing in the tap) preventing the cold pressure to drop enough to cause the cold water pump to turn on. This may only last a few seconds until the pressure is relieved and the pump can then turn on, at which point the cold will flow and mix with the hot to reduce the water temperature.

Quite often the pump can actually deliver more water than the tap can discharge so the pressure can build up again in the pipe work and be enough to cause the pump to turn off. This is characterised as the pump pulsing whilst a tap is open. If it does this , then you are likely to get pulses of only hot water alternating with warm mixed water.

This can usually be resolved by fitting the pressure accumulator to the cold pipework, which mimics the pressure variations in the hot tank when using a mixing tap. It cant stop the initial pulse of hot water, but it can significantly reduce or even eliminate the problem after the first pulse.

The first pulse will usually be moderated to some extent as the hot water will lose some of its heat to the pipework and fittings.

 

[paulweller84]

Based on what you have described, you will definitely benefit from having the Surge Damper/Pressure accumulator included as shown below
View attachment 5119
Here's the reason why it helps:-

Most water heaters in caravans are storage heaters, and they use the cold water being pushed in at the bottom to expel the heated water which accumulates at the top of the tank. The cold water enters through a non return valve which stops the tanks content and pressure from back flowing and emptying through the cold water pipes. The tan is deliberately designed to leave an air cap at the top above the hot outlet pipe. This is necessary to accommodate the expansion of water as its heated.

Initially when you prepare the system you have to fill the heaters tank, by opening a hot tap and allowing the pressure of the cold water to fill the tank.
The cold water flows in and displaces the air in the tank. you know when the tank is full becasue you get a steady flow of water through the hot tap, when you close the tap, it stops the outflow, but the pump will continue to push water in raising the pressure inside the tank and in the cold pipework equally until it reaches the cut off pressure set on the pressure switch .

The cold feed and the cold water in the tank are at the same pressure. When the heater is turned on, as the water temperature rises, it expands, but becasue of the non return valve on the heater input and the closed taps all the expansion has to be accommodated by the air cap in the tank, Consequently the air cap is squeezed and its pressure rises above the water pressure in the cold pipework which is still above the pressure switches threshold.

Once the water is hot, the pressure in the hot side is greater than the cold, so if you open a mixer tap (e.g shower ) the pressure in the hot tank will cause the hot to flow, and it will add some of that pressure to the cold side(through the mixing in the tap) preventing the cold pressure to drop enough to cause the cold water pump to turn on. This may only last a few seconds until the pressure is relieved and the pump can then turn on, at which point the cold will flow and mix with the hot to reduce the water temperature.

Quite often the pump can actually deliver more water than the tap can discharge so the pressure can build up again in the pipe work and be enough to cause the pump to turn off. This is characterised as the pump pulsing whilst a tap is open. If it does this , then you are likely to get pulses of only hot water alternating with warm mixed water.

This can usually be resolved by fitting the pressure accumulator to the cold pipework, which mimics the pressure variations in the hot tank when using a mixing tap. It cant stop the initial pulse of hot water, but it can significantly reduce or even eliminate the problem after the first pulse.

The first pulse will usually be moderated to some extent as the hot water will lose some of its heat to the pipework and fittings.

Thank you for that detailed reply, it's much appreciated and it makes sense. I might call Whale and Monday and put this to them as their Watermaster IC product specifically says it does not need a surge damper, but by what you're saying it's possible it still might. Here's the bit of kit anyway, if you haven't already seen one? https://www.whalepumps.com/rv/produ...=31&FriendlyID=Watermaster-IC-Pump-Controller

 

[paulweller84]

Updated diagrams. Thanks all for the advice. Much appreciated

 

[ProfJohnL]

Thank you for that detailed reply, it's much appreciated and it makes sense. I might call Whale and Monday and put this to them as their Watermaster IC product specifically says it does not need a surge damper, but by what you're saying it's possible it still might. Here's the bit of kit anyway, if you haven't already seen one? https://www.whalepumps.com/rv/produ...=31&FriendlyID=Watermaster-IC-Pump-Controller

The Watermaster IC is designed to modulate the pump speed to negate the surge issue, though it will not control the initial surge of hot water, but neither will the surge damper!

 

[paulweller84]

The Watermaster IC is designed to modulate the pump speed to negate the surge issue, though it will not control the initial surge of hot water, but neither will the surge damper!

What do you think then, leave the damper out?

 

[Jcloughie]

Updated diagrams. Thanks all for the advice. Much appreciated

View attachment 5128

Does the drain valve double as a one-way valve?

John

 

[paulweller84]

Does the drain valve double as a one-way valve?

John

No, as far as i know. If it does, I’d remove the non-return valve adjacent to it

 

[Gafferbill]

....if you are using Whale components then there is a non return valve in the Whale inlet socket for the submersible water pump.

 

[Buckman]

What do you think then, leave the damper out?

We have the onboard tank on our caravan and it has the surge damper fitted as the system also has the onboard pump. There must be a good reaosn for fitting it otherwise to save a penny manufacturers would not be fitting the unit.

 

[JTQ]

We have the onboard tank on our caravan and it has the surge damper fitted as the system also has the onboard pump. There must be a good reaosn for fitting it otherwise to save a penny manufacturers would not be fitting the unit.

Because water is not compressible items like the Whale surge damper are added to give some "compliance", as does the air trapped in the crown of water heaters*, and to a very small extent the pipework being in plastic tubing. This type of surge damper just adds a gas bubble, usually air to give that compliance, something that's compressible.

Without this compliance the pump pressure switched systems would function "harshly" switching on and off way more frequently, responding immediately to the inevitable minor leaks back through the pump non return valve.

Should the inboard pump be a displacement type as opposed to a rotodynamic type as favoured by submersible pump makers, these create a pulsing flow, here the compliance added by a surge damper somewhat smooths the achieved water flow.

They add refinement, thus fitting them or not reflecting where a brand wants to be seen.

Edit * The air in the crown achieves less in this compliance contribution because of the anti hot back flow non return valve needed