Caravan water pressure for showers

[intransient1]

Here we are in freezing Norfolk, sunny sky's and a caravan shower that won't hold its temperature because of low water pressure.
What makes it worse is that it had just been in the dealership for this very problem.
We get fluctuations of boiling bored or freezing cold water.
Well back to the dealership again after new year as there is no user adjustment available.

 

[Grahamh]

Had this problem when I took delivery of our elddis Xplore. To fix it I followed the reset procedure in the manual for the water pump. - haven't got it handy or I would copy it to you. It fixed the problem at the time but I am advised that it can happen again and I may need to reset it again. The water would run for a few seconds then the pressure would fall off and come back repeatedly. There is a red reset button on the inside face of the water inlet point.
hth's

 

[jay1976]

on the feed pipe from aquaroll inside caravan is there a pressure tap if so the screw or thumbscrew on top is for alterating when the pump come on or off this may be faulty or just need adjusting... for cost of a filter if 1 fitted fit a new one in case thats clogged

 

[RayS]

Could you post more details of the pump and water system, as this would help to give advice. The pump may be Whale or Carver or Truma for example The more recent Whale systems have a yellow block on the inside of the socket where the pump plugs into the caravan which has to be calibrated to get the correct pump pressure - not difficult to do but you need to know the sequence of events, These are in the leaflet which comes with the pumps or can be found on the Whale website.

Other systems may have an adjustable pressure switch which will look like a valve in the water line inside the caravan, usually with a knurled knob on the top and two wires going into the body.

Yet other systems have neither of these and the pumped is switched on and off by microswitches fitted inside the taps and shower head. There is no adjustment for these, but this sort of system is less likely to have the pressure fluctuations you describe.

 

[ProfJohnL]

Hello Intransient,

Let me try to describe what I think you may be experiencing. Initially you start to use the shower and at first you get some water for a second or two but the pump has not yet turned on. Then the pump turns on, and you start to get WARM water through. Then after a few seconds the pump turns off and you get a surge of HOT water, then after a few seconds the pump turns on again and the water returns to WARM. This oscillation between only HOT and mixed WARM water flows recurs until either you stop showering.

This effect called surging, and it happens because the pump is controlled by a pressure switch, and the pump is capable of delivering more water than is being used by the shower, and most important of all, the cold water system does not have a surge damper fitted.

The reason this happens is the hot water storage tank needs a small air cap in the tank to allow for the expansion of the water as it is heated. The hot tank also has a non return valve fitted at its inlet, so cold water can be pushed in but wont run back out. Air in the tank not only allows the heated water to expand, but it is also partially compressed when the pump runs. (This is why when you turn a hot tap off the pump usually runs for a few seconds as it recompresses the hot tank)

By comparison the cold system does not have a similar air cap so the cold water pressure response is much quicker to drop when the pump turns off. This means that during a shower if the cold system pressurises and turns the pump off, the cold water flow stops immediately, but the hot water continues to flow because the compressed air cap pushing the hot water out It will continue to push water out until its pressure drops enough to allow some cold water to enter the tank which in turn drops the pressure in cold line and turns the pump on again. And so the cycle continues.

Some more recent water pump systems incorporate some clever circuitry which is designed to modulate the pumps delivery to match the water being used. These should eliminate the surge phenomena provided it is set up correctly. The older pumps need a surge damper to be fitted to the cold pipework. This essentially adds an air cap to the cold supply to match the hot tanks air cap, and thus reduce any rapid pressure differentials between hot and cold supplies.

 

[RogerL]

Pressure switched systems should all have a surge damper by the pressure switch - this, plus the air gap referred to John above should mean that surges NEVER occur - or at least don't occur where the pressure switch is adjusted properly.

 

[intransient1]

Hi Everyone,
Thanks for all the replies.
It is a Whale setup on a 2014 elddis avante 540 without a user adjustable pressure valve.
The really annoying part is that I collected the van back from the dealership just before going on holiday over Christmas and new year and one of the jobs that needed doing was the water pressure which they said they had done.
I will check if there is anything I can do that does not affect the warranty, but it will have to go back again.

 

[Grahamh]

Yes mine just the same, as RayS says you reset the system iaw the user manual at the inside of the water inlet point (red button). I was advised that it can need resetting more than once but it only takes a few minutes to do.

 

[chrisbee1]

I had a similar problem on my 2013 Avante. A quick e-mail to Whale and they sent me a modified controller FOC the next day. Brilliant customer service. Make sure you calibrate the system at the shower with the head at the top of the riser rail.

 

[RayS]

As Graham says, except on my van the button is black not red, and quite small. When you look at the baxk of the inlet sockey, i.e.from inside the caravan, it should have a yellow block about the size of a matchbox attached to it with 3 wires connected. These are for + and - 12v supply and one for the pump running light which you should find incorporated with the pump master switch probably near the door of the caravan.

The set up instructions should be in the Elddis handbook and the whale leaflet supplied with it but if not go to the whale website. It,s quite easy but I appreciate may not look that way first time. If you are stuck for the instructions, re-post and I will type them out here - they are not very long..

 

[RayS]

Since my previous post I have discovered another possible cause of erratic pump behavior. The pump was cycling when the handbasin tap was turned on, giving a surging delivery. This despite having a surge damper fitted.
The taps are made by Whale and if you look at the delivery end of the spout you may see two small flats on the side of the nozzle. If so you can put a spanner on them and gently unscrew the entire nozzle assembly. It's really quite a complex bit of kit - I was expecting just a perforated device, but it contains wire mesh screen with two different sizes of mesh, and a plastic component with lots of through holes. Take careful note of the order in which these components are assembled if you take them apart, reassembly order is not intuative.
The mesh screen were largely blocked with lime scale deposits caused by the very hard water on our usual campsites, and cleaned very easily by soaking in vinegar. I found signs of the same build up in the kitchen tap too.
The surging effect was caused by the pump being able to deliver water faster than it could escape from the tap, with the result the pressure would rise and stop the pump and then fall again and restart the pump within a couple of seconds and so on.
The van has had about 180 days use from new, so those with less use and/or in areas of less hard water may not suffer the same problem, but you could get the same effect from loose bits of plastic from the pipes or anything else which may have got into the system during assembly. Given the poor build quality often reported this is not too difficult to imagine.
The taps in my previous van were, I think, Reich and did not have this removable filter facility, so well done Whale.

 

[RogerL]

The surging effect was caused by the pump being able to deliver water faster than it could escape from the tap, with the result the pressure would rise and stop the pump and then fall again and restart the pump within a couple of seconds and so on.

Then the effectiveness of the surge damper needs questioning - because if you've got a well charged battery, or EHU, and a decent pump that happens all the time with taps partially opened.

Whale's website states:-
"Pump runs intermittently ON, OFF, ON, OFF etc.
Seen as pulsing flow from tap, or as inability to set
constant water temperature, water goes hot, cold,
hot, cold instead of constant warm. Most likely
cause is that present voltage is significantly higher
than when last adjusted.
CURE: Re-adjust pressure switch, if problem
persists add a Whale Surge Damper (WS7205).

http://www.whalepumps.com/rv/siteFiles/resources/docs/resource-library/WhaleAdjustingyourpressureswitchb.pdf

 

[ProfJohnL]

I have given more thought to this and the scenario Ray S reports could be explained as follows:-

Assuming the surge damper adds an air volume to the cold system that roughly equals the air cap in the hot tank, then the surge damper action should mimic the hot tanks pressure drop quite closely provide the same amount of water is being used from both sets of pipework.

In domestic mixer taps, the water from both hot and cold systems is kept separate until it emerges from the taps nozzle. This is so cross contamination of the freshwater supply cannot occur. That is the standard arrangement for WRC approvals of domestic plumbing. Where post valve mixing occurs such as in thermostatic valves, the incoming supplies have to have back flow check valves fitted.

However in Ray's report he tells us the gauze/nozel of the tap was partially blocked. This infers the tap must genuinely mix the water from both hot and cold pipes before it is passed out through the gauze. This is important because it effectively connects the hot and cold pipework together in such a way that pressure can be transferable between the two sets of pipes.

If the cold tap is open more than the hot, it means the cold water pressure will try to drop more quickly than the hot. This may mean the higher pressure in hot system will try to transfer through the taps mixing chamber back into the cold pipe work, and may hold the pressure switch off for longer than is desired, allowing a hot surge from the tap.

If the gauze in the tap is clear, then the problem should be virtually eliminated as minimal pressure will be created in the mixing chamber.

Clearing the debris from gauzes will certainly help, but it may also help to try readjusting the pressure switch.

 

[RogerL]

Not sure if it alters your logic, but don'f forget that the water supply is only the cold system until after the pump, pressure switch and surge damper - only then is a cold feed taken to the hot water system.

Unlike a domestic system where the hot water header tank completely isolates the hot water supply from cold system pressure - and maintains constant pressure eliminating the need for a surge damper.

 

[ProfJohnL]

Hello Roger,

I took into account the fact the cold water system in a caravan supplies the hot tank, but that is through a non return valve. With a partially blocked mixer tap, for the reasons described above any excess hot pressure will begin to affect the cold supply, and could give rise to the effect noted.

My reference to the domestic taps was to point out the fact the water regs require the incoming supply to be protected from any form of back flushing which could contaminate the supply. this is why most mixer taps maintain separate tubes right to the tip of the nozzle.

Following a major health incident many years ago ( and I cant remember when or where) where a cold water tap at a farm had a hose which was turned on and left dangling on the floor. Due to a problem at the pumping station the pump stopped, and the pressure in the mains pipe turned negative ( I assume it was syphonic effects) and the tap that was open started to suck contaminated water back into the main. There were subsequent health issues with other consumers on the same main. Since then double check one way valves have to fitted where there is any possibility of the cold supply being capable of sucking contaminated water back into the pipework.

You are correct about the effectiveness of a separate header tanks for domestic hot water (and cold water for showers) systems by maintaining a near constant head height and thus system pressure. Also the float valve system with its open vent will tend to isolate the incoming supply from the tank water. This is necessary not only to prevent over pressure on the but as the water company has no control over the conditions of the storage tank it could be come infected with for example legionella and other bacterial contaminations. So even though the risk of siphoning back is small the incoming still needs to be double checked.