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On Board Water Pressure Help


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Hi all, looking to gain a bit of knowledge and advice on water pressure.

Long story short, the domestic water pressure on our boat is useless, it starts out weak, the pump eventually kicks in, you get a good blast for nearly a minute and it then slows to a trickle over the next minute or two. Really irritating for washing up, and pretty unpleasant when showering as it goes from boiling hot high pressure to a freezing cold drip shortly after!

We had a new parmax 4 water pump fitted but there's no difference, arguably it's a little worse. Previously, running the cold tap in the bathroom gave the shower some consistency but that doesn't work with the new pump!

I'm afraid I don't know if we have an accumulator, in fact I know very little about the domestic water system πŸ€”Β 

Can anyone give any thoughts on where we should start in trying to solve the issue?

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I assume you have a pressure vessel and this must first be set at the right air pressure. Β Very often these are set too high. Normal pressure is about 1 BAR. Β Best done by taking a small portable air compressor on board, which has a tyre pressure gauge. Β This may make a big improvement before you go any further.

You may then have a Square D pressure switch, which I can tell you how to adjust, but it is not easy!

Some photos of what you have got would be a great help.

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I forgot - you have to set the air pressure with the water pressure at zero. So water pump off and taps open.

It sounds to me as though the pump cut in pressure is too low. Β But first you have to get the air pressure right. Β You then set the cut OUT pressure a little bit (about 2psi) below the air pressure. Β With the shower running with both taps open, you then bring up the cut IN pressure until it runs constantly.

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Hi Simon first check that the air pipe to the top of the tank is clear and the gause mesh on outside of the hull fitting is clear, then follow the pipe to check it hasn't been kinked and if rubber the inside of hose could be collapsed replace with plastic water hose. Then ditto what Vaughan has said. John

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Thanks both for the replies. @OldBerkshireBoyΒ it doesn't sort itself out at all, remains the same as long as you're trying to run taps/showers.

@VaughanΒ fantastic guidance, thank you. I believe a pressure vessel is the same as an accumulator tank, and I don't know if we have one. When we're on board I'll dig around and take a load of photos. Assuming I can find the right bits I'll follow your advice (or ask our marina to investigate beforehand) and see how it goes.Β 

I take it there's a valve or something on the pressure vessel to check the pressure etc.Β 

Just to make sure I understand (!) - water pump off and taps open. Set the pressure vessel to 1 BAR (is that right, about 14 psi??). Set water pump cut OUT pressure about 12 psi. Turn the pump on, run the shower. Adjust cut IN pressure until consistent flow at the shower. I believe there's a pressure adjustment screw on the top of the pump.Β 

Is that about right?

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12 minutes ago, annv said:

Hi Simon first check that the air pipe to the top of the tank is clear and the gause mesh on outside of the hull fitting is clear, then follow the pipe to check it hasn't been kinked and if rubber the inside of hose could be collapsed replace with plastic water hose. Then ditto what Vaughan has said. John

Good plan, thanks. I did wonder if it could be something as simple as a blockage somewhere, so I'll plan to investigate. If nothing else I might start to figure out what and where all the relevant bits and pieces are!

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A good plan is to get a a4 size folder with plastic leafs so you can make diagrams, info etc when you come across these, also a fuse diagram is very helpful along with a wiring diagram with cable colours. doing it now while you can see, bend and remember what previous owner told you, and before everything fades, along with your memory. John

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Hi Simon the pressure vessal is userly red or blue in colour and is fitted after the pump in the supply hose connected by a tee piece on the top you have a valve the same as a car Tyre valve on your car, depress the pin to let out air and pump in air to increase pressure you can use a car pressure gauge to check the pressure, think car Tyre. John

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Another way of doing this, is if your pump comes with a built in pressure switch. Β This should indicate what the cut in and cut off pressures are. Β In this case, set the air pressure at 2psi above the cut off pressure given for the pump.

You mentioned talking to the marina about it and this is probably a good idea as it is a complicated job to get right but it Β  shouldn't cost more than an hour's labour.

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Thanks John, that's pretty much what I thought re the pressure vessel. All I have to do is find it!

And Vaughan, thanks for your further input, I'll find some manuals for the pump and do a bit more reading up to see how far I can stretch my understanding. Agree with your point about the marina although I'm keen to learn, I really should know a bit more about it!Β 

As the marina fitted the new water pump, should we have expected them to make sure everything was correctly set up and running properly?Β 

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4 hours ago, Regulo said:

How are your finances? 😁. If you want to spend, rip it all out, and put in a variable speed pump - no need for accumulator tank, and constant pressure at all times. 

:8_laughing::8_laughing::8_laughing:

Does anyone want to spend?!Β 

Don't fancy ripping it all out, especially if it's an easy fix and considering we've only just had a new water pump fitted. Out of interest are variable pumps any good, reliable etc?

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16 hours ago, simonp said:

As the marina fitted the new water pump, should we have expected them to make sure everything was correctly set up and running properly?Β 

I think I would have expected them to 'test' the system to make sure it was all ok. Certainly worth going back and asking them the question!

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19 hours ago, simonp said:

As the marina fitted the new water pump, should we have expected them to make sure everything was correctly set up and running properly?Β 

That really depends on the wording at the time.

Hello, I need a new water pump fitted please - New pump fitted.

Hello, Im having problem with water flowing to taps & shower, - Whole different thing.

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15 hours ago, simonp said:

Β Out of interest are variable pumps any good, reliable etc?

Fitted one on my boat, and had no trouble in the 3 years before I sold it. They give a constant flow at the taps/showers, with no temperature fluctuations. Wish I'd done it years previously, totally transformed the water system performance.Β 

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  • 3 weeks later...

Hi all, coming back to this, here are some photos of the water components I can see. It also appears we have a pumptron box as well which I think is the pressure switch.Β 

It appears that the red pressure vessel may not be in use at all. I can feel water in the pipe to the pressure switch when the pump operates but none in the blue hose underneath the pressure vessel.

Does this make sense to anyone?

Β 

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Β 

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I can see two problems at once :

1/. The black elbow pipes on either side of the pump are not food quality. Β They look as though they come off an engine. Β I would replace these for hygiene. Β Also clean the inline filter from the tank.

2/. The new pump you have bought has its own pressureΒ switch, but you also have a Unitron "Square D" pressure switch in the line. Β You can't have both. Β Personally, I would bypass the wiring in the pump pressure switch and carry on with the Square D.

On top of the red pressure vessel is a round plastic cap. Β Unscrew this and you will find a bicycle type air valve inside. This is where you check the air pressure, as we have already described.

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Personally I'd do as Ray suggested. That in line filter looks a bit grotty inside.

If that was my boat I'd remove everything back to the tap coming out of the tank. I would then fit a T piece with another tap and a hose going down into the bilge. This will allow you to easily drain down your tank for the Winter or to replace the water if the boat has been left standing a few weeks without having to pump the whole tank through the taps. Next take Blue food grade hose from the other outlet on the T piece to a new variable speed pump. The latest Jabsco ones will come with a new in line filter that clips directly onto the inlet of the pump. Finally take the output from the pump in Blue food grade hose to supply your taps / hot water calorifier.

Result, much simpler system, easier to maintain and consistent temperature water at any flow rate.Β 

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31 minutes ago, Meantime said:

Result, much simpler system, easier to maintain and consistent temperature water at any flow rate.Β 

Don't forget also, a non return valve on the cold feed to the calorifier tank. This tank also needs a pressure relief valve (PRV) on the hot outlet.

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