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Mains water pump


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Heya,

 

I'm looking to amp up the water flow rate in the boat by adding in a mains pump to the system - we're on shoreline pretty much all the time, so power isn't an issue.

 

Currently there's a parmax2.9 Jabsco installed with an accumulator, and we'd keep that as-is so that we can switch back when we're on the batteries. It's 25PSI (1.7 bar), so this looks like it would suit without blowing the pipes apart, and it has about twice the flow rate of the Jabsco

 

Here's the old layout and a rough plan of what I think might work for the new one:

image.png.2a95ca44fd4227677119a2eace5bdc26.png

 

 

Before I go and order the pump, is there anything in this setup that looks off? The pump not in use will be turned off so they won't fight against eachother, but do they need their own individual stopcock to prevent the other pump putting negative pressure on the seals etc.?

 

Cheers,
Jacob

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Why not put two parmaxes plumbed and wired in parallel? That should double the flow rate without the need for switching, and gives you a fail safe if one pump fails. As the cut in and cut out pressures on the two pumps will not be exactly the same, one will probably do the lions share, with the other only cutting in when the flow is highest.

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I'm not convinced that mixing a diaphragm pressure pump and a centrifugal pump is going to work without at least some isolation, though that could simply be an "L" port valve joining the two  outlets, (the handle of which could operate a switch controlling which pump ran), but don't forget to consider the size  of the inlet - that pump has a 22mm inlet, if the pipe from your tank is 15mm it will restrict the flow, less of a problem if the pump is close to the tank but could be significant if the pump is some distance from the tank, any filters or valves in the line may also restrict flow.

 

springy 

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Cheers for the replies

 

20 minutes ago, David Mack said:

Why not put two parmaxes plumbed and wired in parallel? That should double the flow rate without the need for switching, and gives you a fail safe if one pump fails. As the cut in and cut out pressures on the two pumps will not be exactly the same, one will probably do the lions share, with the other only cutting in when the flow is highest.

Good shout, hadn't thought of that - I assume they've both feed into the accumulator?

 

6 minutes ago, springy said:

I'm not convinced that mixing a diaphragm pressure pump and a centrifugal pump is going to work without at least some isolation, though that could simply be an "L" port valve joining the two  outlets, (the handle of which could operate a switch controlling which pump ran), but don't forget to consider the size  of the inlet - that pump has a 22mm inlet, if the pipe from your tank is 15mm it will restrict the flow, less of a problem if the pump is close to the tank but could be significant if the pump is some distance from the tank, any filters or valves in the line may also restrict flow.

Both pumps will be right next to the tank, so the change shouldn't be an issue. Will look into L valves

7 minutes ago, blackrose said:

Or why not just get a higher pressure Parmax pump and avoid the complexity of two pumps?

I've had a look at the parmax range, and the highest 12v flow rate @ 25psi (from what I can see) is 11lpm, which is our current one. I don't want to increase the pressure because I'm not sure what the rest of the system is rated for, so I'll play it safe and keep any alterations under 25psi to avoid a leak

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2 minutes ago, blackrose said:

Or why not just get a higher pressure Parmax pump and avoid the complexity of two pumps?

Higher pressure does not increase flow rate. Your 2.9 delivers 11 litres per minute. There are lots of options that deliver up to 20 litres per min. or more. Just be aware, if using one, your water tank will empty a lot quicker. It is too easy to let more water in than you intend.

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3 minutes ago, Ex Brummie said:

Higher pressure does not increase flow rate. Your 2.9 delivers 11 litres per minute. There are lots of options that deliver up to 20 litres per min. or more. Just be aware, if using one, your water tank will empty a lot quicker. It is too easy to let more water in than you intend.

 

We're at a marina with a tap 2m away so can have the luxury of long showers ;)

 

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1 hour ago, jacob said:

I'm looking to amp up ............

 

I presuming this has some modern language connotation - maybe you can explain. (remember that 90% of the forum members are over 65 years of age)

Do you simply mean to increase the flow rate ?

 

To 'amp up' I would have thought meant to increase the number of amps.

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The pump linked to says it's a shower pump and says absolutely nothing about duty cycle. Just consider if operating it as a domestic water pump and ifi t has its own pressure switch to turn it off when the system is up to pressure. I know our home shower pump does not.

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1 hour ago, Ex Brummie said:

Higher pressure does not necessarily increase flow rate. Your 2.9 delivers 11 litres per minute. There are lots of options that deliver up to 20 litres per min. or more. Just be aware, if using one, your water tank will empty a lot quicker. It is too easy to let more water in than you intend.

 

I took the liberty of inserting a word into your post. Higher pressure can increase flow rate to some degree. My Parmax 3.5 40psi pump has a flow rate of 13.2 litres per minute. Not adequate for the OP's requirements but I didn't realise he needed to increase flow rate that much when I suggested a higher pressure pump.

Edited by blackrose
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How are you going to switch the second  pump?  Shower pumps usually work on a flow switch, which is triggered by initial flow caused by the mains or header tank pressure.   They also have no non return valves, because the pump does not have to prevent flow when off. So any pressure in the accumulator will dissipate through the shower pump once it is off and will not trigger a flow sensor when next you open a tap.

 

 Additionally, the Parmax  when in use,  will pump backwards through the shower pump because there is no non return valve.

 

The extra Parmax suggestion above  is a good one, and would be best if you installed a separate pressure switch as well -Square D are good- to control both pumps together.  The pumps can share the accumulator which needs to be down stream of both pump outlets.  Not quite  as shown in your diagram though- the accumulator should be tee'd into the pipe to the taps etc. 

 

N

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We have a salamander pump at home and it does not have a non return valve, and being centrifugal I don’t think it has any back flow prevention, so when the Parmax operates it will flow back through the salamander pump.

The salamander also has an internal flow rather than pressure switch so the parmax would have to be turned off otherwise the system pressure would prevent the salamander pump operating.  Basically I don’t think it is a suitable pump

 

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1 hour ago, Alan de Enfield said:

 

I presuming this has some modern language connotation - maybe you can explain. (remember that 90% of the forum members are over 65 years of age)

Do you simply mean to increase the flow rate ?

 

Apologies - I'll flick the 'youth speak' switch off :)  Amp up = needs more oomph - we young people have been mollycoddled to expect, nay, demand, a powerful 30min shower twice a day

 

So it looks likes the best solution is to add an extra Jabsco to the mix  (and it's also about £200 cheaper) - should I install it in series or parallel? My gut tells me that having one pump feeding into the next would be a bad move, but it's been wrong before...

 

image.png.d1dac303ecdfcce85a75826b79693be8.png

 

 

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Has to be parallel to increase flow. Output in series will be the same as one pump and might damage the second one.

 

Check the shower drain pump can handle the extra flow rate !

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Lower diagram is the only way to get any gain.

  As above, to prevent the pumps internal switches 'fighting' each other fit a single, stand alone, pressure switch in the delivery line, after  the acc ideally, and use this to switch both pumps.  A Schneider square D has two sets of contacts so you can use one set for each pump.

N

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I take it this is for your shower. When you use the shower do you know if the pump supplying the water runs continually from when you start the shower until after you switch the shower off? You may not be able to hear it in the shower and may need someone else to listen to it for you.

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What is the actual flow rate at the shower? Try measuring how long it takes to fill a bucket with a known volume to get the real litres/minute. You may find that the limiting factor is the pipework, not the pump. I have an 11l/min pump, but the actual flow rate to taps is around 6l/min. My plumbing uses 15mm OD pipework throughout. It may be that a better solution is to increase the pipe diameter to the shower, or wherever else you want more flow. Need to measure first. The 11l/min is for the pump with no pipework connected to it. The longer the pipes, the more corners and fittings and the narrower the bore, the less water gets through. If the pipework is too restrictive, then more oomph on the pump won't make much difference.

Jen

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4 hours ago, jacob said:

 

Apologies - I'll flick the 'youth speak' switch off :)  Amp up = needs more oomph - we young people have been mollycoddled to expect, nay, demand, a powerful 30min shower twice a day

 

So it looks likes the best solution is to add an extra Jabsco to the mix  (and it's also about £200 cheaper) - should I install it in series or parallel? My gut tells me that having one pump feeding into the next would be a bad move, but it's been wrong before...

 

image.png.d1dac303ecdfcce85a75826b79693be8.png

 

 

Why not move into a house as they have unlimited water supply and are purpose built to waste water?

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7 hours ago, Alan de Enfield said:

 

I presuming this has some modern language connotation - maybe you can explain. (remember that 90% of the forum members are over 65 years of age)

Do you simply mean to increase the flow rate ?

 

To 'amp up' I would have thought meant to increase the number of amps.

Just imagine the letter R and it makes sense .

Can't remember my 65th birthday

Edited by Slim
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13 hours ago, mrsmelly said:

Why not move into a house as they have unlimited water supply and are purpose built to waste water?

 

I will get right on that, cheers :)

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21 hours ago, jacob said:

Heya,

 

I'm looking to amp up the water flow rate in the boat by adding in a mains pump to the system - we're on shoreline pretty much all the time, so power isn't an issue.

 

Currently there's a parmax2.9 Jabsco installed with an accumulator, and we'd keep that as-is so that we can switch back when we're on the batteries. It's 25PSI (1.7 bar), so this looks like it would suit without blowing the pipes apart, and it has about twice the flow rate of the Jabsco

 

Here's the old layout and a rough plan of what I think might work for the new one:

image.png.2a95ca44fd4227677119a2eace5bdc26.png

 

 

Before I go and order the pump, is there anything in this setup that looks off? The pump not in use will be turned off so they won't fight against eachother, but do they need their own individual stopcock to prevent the other pump putting negative pressure on the seals etc.?

 

Cheers,
Jacob

Hi Jacob my boat has had a mains water pump from day one, excellent bit of kit ,I can shower people across the other side of the cut if I want! Forgot the make but its been very reliable 10 years plus I think? Don't try to use a shower pump they won't last as that was what was fitted at the beginning. 

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Thinking a little further along your query, a shower pump is designed to boost just that. If you are happy with the water supply elsewhere, then a shower pump fitted in the shower supplies only will resolve your dilemna. Before doing anything, check what volume your shower head will pass, and also bear in mind the capacity of your calorifier. A semi-serious shower pump would empty most boat calorifiers in about 3 -4 mins flat.

Edit to add: For any pedants, I was educated before 1980 and refuse to accept the american spelling of dilemna.

Edited by Ex Brummie
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Not sure we have definitely established a calorifier provides hot water but if its an instant gas heater I think the flow from the shower will be far worse than  a power shower whatever the OP does. If he managed to increase the flow he would probably have cold or tepid water.

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2 minutes ago, Tony Brooks said:

Not sure we have definitely established a calorifier provides hot water but if its an instant gas heater I think the flow from the shower will be far worse than  a power shower whatever the OP does. If he managed to increase the flow he would probably have cold or tepid water.

A cold very powerful shower would be just the thing as the OP would be unlikely to want to stay underneath it for very long, saving water overall. ?

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