Opening up a question to the font of all knowledge that is the Ducati Forum. Looking for a possible reason for the issue please so I may address it and fix it. Our water pump has started acting strangely lately and won’t turn on when water is demanded from outlets which are uphill of it. When water is demanded from outlets which are downhill the water flows under gravity and then the pump kicks in about 1-2 seconds later. The water system in our house is a pressurised system (3bar) driven by an external pump which sits between an external water tank (c.2000 litres) and the house. The external water tank is filled from the well (via the well pump) and holds the water which feeds all outlets in the house except the kitchen sink which runs straight off the well. Downstairs outlets are below the level of the external water tank, upstairs outlets are above the level of the water tank. I have already checked the pressure switch in the pump which is fully functional so I believe I can disregard that as the issue. In theory when a tap is opened the pressure in the system drops as the water flows out which should cause the pump to kick in. However, what’s happening is that when an upstairs tap is opened nothing comes out. When a downstairs tap is opened the water flows under gravity then the pump kicks in. Now any tap upstairs can be opened and all is fine. Consequently, to use the bathroom/shower etc we have to open an outlet, go downstairs, open a tap, the pump kicks in, close the tap and run back upstairs . Counts as morning exercise I suppose but SWMBO is getting a little fed up with it all (#metoo ). All suggestions/help/advice gratefully received.
How hard is it to change the pressure switch? It sounds like the smaller pressure drop from opening an upstairs tap isn’t now triggering the pump.
Sounds like the pump works fine, but it needs priming before it can operate. As I am guessing it all worked fine previously, maybe you either have a leak so the pressure is falling and is subsequently is raised by gravity fed water or that pressure switch appears to be fine -but isn't... Are those switches expensive/ hard to fit?
if your water pump has a small pressure vessel check its got a full charge of air, around 1 bar is normal and its pumped up through normal car tyre vavle,
It should be easy enough to change the pressure switch, Id just have to cut & resolder the wires but I it were the switch why would it work when water starts to run through the pump under gravity . This is one of the things I can’t get my head around. Re the pump needing priming @Jez900ie there are no leaks in the pump area and if I remove the small screw on cap which is used to fill the pump to make sure it is primed, water gushes out so I don’t think it’s that. Also if there were a leak in the system the pump would run continuously as it attempts to maintain the pressure within the system, the whole DW system being pressurised at 3 bar, so I’m pretty sure it’s not leaking anywhere. Re the switch, the default position is on; pressure in the system pushes a plunger against the switch which switches it to the off position. Thus when the system is fully pressurised the pump is off. When an outlet is opened the water flows (due to it being pressurised) the pressure in the system drops, the plunger can now, as it has a spring behind it, move off the switch, causing the switch to go to its default position of on, and the pump turns on and attempts to repressurise the system again, which it fully achieves a short time after the outlet is closed. It’s perplexing the hell out of me.
It does have a small pressure vessel I did check that had air in it and not water ie the diaphragm had split but I shall go and check the actual pressure of it, thanks. What exactly is the purpose of that air vessel?
They tend to fall off the wall when the diaphragm fails and they fill up with water! I imagine they take out the pressure fluctuations when the pump switches on and off.
They are a accumulator so they will fill with water until a equilibrium of pressure is achieved. When there is a surge in flow i.e. you open another tap and the pressure starts to drop momentarily the stored water and energy in the accumulator will compensate to stop cavitation of the pump.
They take the hydraulic shock out of the system, acting like a cushion. Also they set the back pressure of 3 bar for the water, making the switch in the neutral/off position. Once you open a tap the pressure will drop and the switch will turn on. I assume you must have a one way valve somewhere or the pump would kick in periodically when the water lets by the pump head?
Water pressure increases at a rate of 1 bar per 10 metres head, all I can this of is the head on the upstairs taps is sufficient to keep the pressure valve contact open. Is there an adjuster that you can alter to change the trigger point of the switch.
Pump update: Air vessel was removed, had about 1 bar in it, now has 2 bar less 2-3psi, pump pressure switch is set to trigger pump on at 2 bar, so if my research is correct the air vessel should be a couple of psi less. Still no joy . The only thing I hadn’t pulled apart was the water flow switch, part #18 in the diagram. This sits on the inlet side. As the pump has a dry running protection device I presume it’s this. The switch is an impeller that sits in the inlet flow and spins as water passes around it. It contains a magnet which is what creates an electric field as it spins thus triggering the switch and informing the ECU of the pump there is indeed water flowing into the pump. Took it apart, cleaned it all up - we have a high manganese content in our water here which deposits brown sludge over time - and put it all back together. Still nothing Took the water flow switch apart again and rebuilt it again, still nothing; no pump kicking in when the upstairs tap is opened. Clearly, as water is demanded the impeller is supposed to spin around due to the water passing around it but it’s not. Approaching it from a logical and technical point of view I decided it’s sticking so I applied a size 11 solution and stuck the boot in. Lo and behold the pump came on. To prove it wasn’t just a fluke the tap was turned off and then turned on again, no flow, kick the pump by the water flow switch, pump comes on. Repeat a couple more times just to prove the theory. Same thing each time. This then explains why when a downstairs tap is turned on the pump kicks in a few seconds later rather than straight away; gravity causing the water to flow and turn the impeller thus tripping the switch and starting the pump. Quite why the impeller is sticking is an unknown at present as it’s free to move and does move once kick started. However I shall have to see if I can get some replacement parts for the switch & impeller or whether I have to buy a whole new pump .
It just occurred to me, as Im unlikely to be able to buy any spares - the pump brand is Tucson, made in PRC and I can’t find it online - perhaps there’s a way to bridge the connections in the switch to fool the ECU into thinking water is flowing through there
There do appear to be Tucson SBP100 water booster pumps available on line @West Cork Paul https://www.macblair.com/amfilerating/file/download/file_id/3125/ Pressure Switch adjustment is on page 23 and A1 to A3 on page 24.
Read the title, thought it was a Harley question.Sorry, know nowt about domestic water pumps, hope you find a solution.
