Water pump choice from roof level tank

[sometimewoodworker]

We will be installing a water tank about 3 meters above most of the outlets (sinks taps, toilets, shower heads etc) so will need a pump to get good pressure. 

 

The question is which pumps will allow a reasonable flow through them when the power is off. 

 

We often have power cuts of several hours so that's why we are installing a tank in the roof so we will still have running (or maybe walking) water when the inevitable power cut happen.

 

FWIW I am letching after a Mitsubishi inverter even though it's about 3 times the price of a comparable regular one as it wouldn't short cycle with a restricted flow.

[RichCor]

What size tank, what size piping?

How many taps (open at the same time)?

What kind or pressure (or flow rate) are you wanting for the shower?  

 

(for some odd reason some people want firehose-like pressure in their shower of 3-5 bars (45-75 psi), or flow rates above 15 L/min. For that you'll definitely need a pump. 

 

Otherwise, some people do fine with a 'gravity fed' system, if the tank is way above the taps and using 1" (25mm) most of the way and converting down to 1/2" as close to the tap as possible.

 

If you do decide to put in a pump, you can always plump in a bypass with a non-return (anti-siphon/backflow-preventer) around the pump so the water can take either path (through or around the pump) automatically. 

[sometimewoodworker]

7 hours ago, RichCor said:

What size tank, what size piping?

How many taps (open at the same time)?

What kind or pressure (or flow rate) are you wanting for the shower?  

 

(for some odd reason some people want firehose-like pressure in their shower of 3-5 bars (45-75 psi), or flow rates above 15 L/min. For that you'll definitely need a pump. 

 

Otherwise, some people do fine with a 'gravity fed' system, if the tank is way above the taps and using 1" (25mm) most of the way and converting down to 1/2" as close to the tap as possible.

 

If you do decide to put in a pump, you can always plump in a bypass with a non-return (anti-siphon/backflow-preventer) around the pump so the water can take either path (through or around the pump) automatically. 

Hi

 

My question is not to do with pump sizing or a need for one. As I've got instant water heaters I need one. It is which pumps allow water to flow through them when they are off. If there is a style that permits this then I don't have to bother with a separate non-return valve and associated pipe and the potential failure point that it introduces. 

 

We are not expecting to be able to have good pressure showers (or possibly any) when the power is off. Also the water hight head (2 to 3 meters depending on how full the tank is) is fixed and so clearly does not give enough pressure (.2 to .3 bar) for normal use.

 

FWIW my pipes are welded 32mm PP-R and step down at the point the exit the wall into shower, sink or washbasin taps.

 

[canuckamuck]

Usually it would be simple enough to put in a bypass. With either a valve to engage it or a non return valve on the tank feed. But it seems you dont want to go that route.


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[sometimewoodworker]

1 hour ago, canuckamuck said:

Usually it would be simple enough to put in a bypass. With either a valve to engage it or a non return valve on the tank feed. But it seems you dont want to go that route.


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I will if it's the only way but If I don't need to I would prefer not.

[Crossy]

Any pump is going to allow flow through when it's not running (OK assuming it's not a positive-displacement type).

 

Just how much is debatable, an open rotor, single stage, centrifugal is almost unimpeded, but something multi-stage with closed rotors is going to add significant resistance.

 

Try it without the bypass, you can always add one later if needed.

 

[sometimewoodworker]

59 minutes ago, Crossy said:

Any pump is going to allow flow through when it's not running (OK assuming it's not a positive-displacement type).

 

Just how much is debatable, an open rotor, single stage, centrifugal is almost unimpeded, but something multi-stage with closed rotors is going to add significant resistance.

 

Try it without the bypass, you can always add one later if needed.

 

Thanks, and AFIK all of the common domestic pumps are centrifugal.

 

So I'll need to talk to Mitsubishi or find someone who has the inverter to check how much flow is possible 

[Crossy]

5 minutes ago, sometimewoodworker said:

Thanks, and AFIK all of the common domestic pumps are centrifugal.

 

Certainly I know of none that are positive-displacement (someone will find one now) but a lot of the very small ones are peripheral pumps, but they let water flow when off just like a closed rotor centrifugal.

[Wirejerker]

Why not look at putting a Small DC pump that switches over to when the power goes out that will give you "walking water" when power comes on it switches back to AC pump. Can possibly be done with 12 volts but definitely with 24. It's got to be easier than the tank on the roof. But if you already made up your mind.......


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[VocalNeal]

I cannot see the point of an inverter on a water pump for domestic on/off use? If the pump was in constant use but the flow rate changed then yes but for toilet flushing, showers etc. I don't see it. 

Regular on/off Mitsubishi type pumps have and are being used for decades. The tank rots away long before the motor or the pump wear out. 

 

Just unplugged a "conventional" Mitsubishi pump and it will flow water. But if you only have 3m head don't expect much. 

 

Flow rates for Mitsubishi Water Pumps "are all on the interweb.

 

 

[Artisi]

For me I would look at a standard end suction centrifugal pump selected for the flow and head you elect, fitted with a Bio 2000 flow /pressure unit. Switches on at pressure drop and run until no flow sensed.

Would think an end suction would have less restriction than a regenerative turbine unit which all the standard pressure units are. 

[sometimewoodworker]

3 hours ago, Artisi said:

For me I would look at a standard end suction centrifugal pump selected for the flow and head you elect, fitted with a Bio 2000 flow /pressure unit. Switches on at pressure drop and run until no flow sensed.

Would think an end suction would have less restriction than a regenerative turbine unit which all the standard pressure units are. 

Would you like to give an English translation please :0

[sometimewoodworker]

5 hours ago, VocalNeal said:

I cannot see the point of an inverter on a water pump for domestic on/off use? If the pump was in constant use but the flow rate changed then yes but for toilet flushing, showers etc. I don't see it. 

Regular on/off Mitsubishi type pumps have and are being used for decades. The tank rots away long before the motor or the pump wear out. 

 

Just unplugged a "conventional" Mitsubishi pump and it will flow water. But if you only have 3m head don't expect much. 

 

Flow rates for Mitsubishi Water Pumps "are all on the interweb.

 

 

Well well the point of an inverter pump is to have a constant pressure independent of the flow rate. 

 

You  can also adjust the pressure they supply on the Mitsubishi one.

 

Currently (with our old setup) to to get a hot enough shower in the cold season the flow has to be throttled down so far that the pump cuts in and out.

 

I haven't seen any flow rates for pumps that are switched off so since you say they are "are all on the interweb" could you tell me how to find them?

 

I know that with a pressure of 0.2 to 0.3 bar I won't get  much flow but it will be enough to slowly fill toilets and continue hand washing. It may even be enough to rinse of the soap in the shower if the power cuts at just the wrong moment.

[sometimewoodworker]

11 hours ago, Wirejerker said:

Why not look at putting a Small DC pump that switches over to when the power goes out that will give you "walking water" when power comes on it switches back to AC pump. Can possibly be done with 12 volts but definitely with 24. It's got to be easier than the tank on the roof. But if you already made up your mind.......


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That is probably getting too involved for the number of times the power goes out.

 

The tank in the roof should be enough. Of it isn't then the bypass valve might and if that doesn't do it then I may have to do something like that.

 

time will tell

[Artisi]

1 hour ago, sometimewoodworker said:

Would you like to give an English translation please :0

Does this help

[sometimewoodworker]

7 hours ago, Artisi said:

Does this help

It certainly explains your post, and could well be usefully used in feeding water to the tank in the roof space.

 

I  don't know if it would be any better (or cheaper) than one of the more usual Mitsubishi  EP series pumps as you would need to add some kind of pressure tank to equal the functions of that kind of pump. It certainly would lack any of the more advanced functions of the inverter series, 

[Artisi]

1 hour ago, sometimewoodworker said:

It certainly explains your post, and could well be usefully used in feeding water to the tank in the roof space.

 

I  don't know if it would be any better (or cheaper) than one of the more usual Mitsubishi  EP series pumps as you would need to add some kind of pressure tank to equal the functions of that kind of pump. It certainly would lack any of the more advanced functions of the inverter series, 

You can add a pressure tank to handle the small on / off scenarios - the glass of water etc. The pump would start on pressure drop and then run until requirement ceases, ie.  close tap. 

The Brio website will help. 

[sometimewoodworker]

45 minutes ago, Artisi said:

You can add a pressure tank to handle the small on / off scenarios - the glass of water etc. The pump would start on pressure drop and then run until requirement ceases, ie.  close tap. 

The Brio website will help. 

And how does that make it better or cheaper than the standard pumps which include all of that's?

[Artisi]

8 minutes ago, sometimewoodworker said:

And how does that make it better or cheaper than the standard pumps which include all of that's?

Just answering your original question, I would think the flow restriction thru' an end suction pump is less than the regen. type pump. Plus this arrangement won't hunt on and off as it senses flow not pressure. 

Also check Grundfos, from memory there is a flow sensing pump unit in their bag of tricks. 

Correct, probably more expensive  than the normally used pumps, but over 10 years it doesn't amount to much. 

[VocalNeal]

On 5/9/2017 at 9:02 PM, sometimewoodworker said:

Currently (with our old setup) to to get a hot enough shower in the cold season the flow has to be throttled down so far that the pump cuts in and out.

Exactly why people up north need "bigger" shower heaters than people in BKK. Your water temperature for your shower has to do with your shower heater being to "small" 

In BKK one might get away with 3500kW or 4500kW if you want really hot showers  Up country you need 6000 kW -ish

 

Also sounds like your pump is over sized.

[Artisi]

10 minutes ago, VocalNeal said:

Exactly why people up north need "bigger" shower heaters than people in BKK. Your water temperature for your shower has to do with your shower heater being to "small" 

In BKK one might get away with 3500kW or 4500kW if you want really hot showers  Up country you need 6000 kW -ish

 

Also sounds like your pump is over sized.

I upgraded from 3xxx to 4500w for the winter months, it is sufficient in Phitsanulok.

[sometimewoodworker]

7 hours ago, VocalNeal said:

Exactly why people up north need "bigger" shower heaters than people in BKK. Your water temperature for your shower has to do with your shower heater being to "small" 

In BKK one might get away with 3500kW or 4500kW if you want really hot showers  Up country you need 6000 kW -ish

 

Also sounds like your pump is over sized.

With an EP-155QS as the pump it's the smallest available it's not over size.

[Artisi]

8 hours ago, VocalNeal said:

Exactly why people up north need "bigger" shower heaters than people in BKK. Your water temperature for your shower has to do with your shower heater being to "small" 

In BKK one might get away with 3500kW or 4500kW if you want really hot showers  Up country you need 6000 kW -ish

 

Also sounds like your pump is over sized.

The heaters would be rated as w not kW. 

[Crossy]

58 minutes ago, Artisi said:

The heaters would be rated as w not kW. 

 

Actually it's a capital W for watts.

 

But I agree, a 6 megawatt (6000kW) heater is a little over the top

 

[Artisi]

1 hour ago, Crossy said:

 

Actually it's a capital W for watts.

 

But I agree, a 6 megawatt (6000kW) heater is a little over the top

 

not if you want to service the whole street :)

[VocalNeal]

2 hours ago, Crossy said:

But I agree, a 6 megawatt (6000kW) heater is a little over the top

Crossy.  My typo should read 3500W, 4500W and 6000 W. Given that a kettle is about 1500W . I started with 3.0 and 4.5 changed the numbers but not the "k"

 

However I think everyone understood. 

 

5 hours ago, sometimewoodworker said:

With an EP-155QS as the pump it's the smallest available it's not over size.

So the heater is too small?  Jut checked mine. As I remembered it is 4500 and in BKK. "Electronic" control whatever that means. A small light comes on when it reaches set-point. 

 

I guess I could add that it doesn't hurt to back flush with vinegar once in a while as they will get "furred" up just like a kettle and the efficiency goes down. Depending on one's water type!

[Artisi]

39 minutes ago, VocalNeal said:

Crossy.  My typo should read 3500W, 4500W and 6000 W. Given that a kettle is about 1500W . I started with 3.0 and 4.5 changed the numbers but not the "k"

 

However I think everyone understood. 

 

So the heater is too small?  Jut checked mine. As I remembered it is 4500 and in BKK. "Electronic" control whatever that means. A small light comes on when it reaches set-point. 

 

I guess I could add that it doesn't hurt to back flush with vinegar once in a while as they will get "furred" up just like a kettle and the efficiency goes down. Depending on one's water type!

Also check any inline filters. 

[Crossy]

59 minutes ago, VocalNeal said:

Crossy.  My typo should read 3500W, 4500W and 6000 W. Given that a kettle is about 1500W . I started with 3.0 and 4.5 changed the numbers but not the "k"

 

However I think everyone understood.

 

Of course, my tongue was planted firmly in my cheek :)

 

[VocalNeal]

3 hours ago, Artisi said:

Also check any inline filters. 

And dunk the shower head in some Coca-Cola? But that would increase the water flow

[Gary A]

When we moved upcountry to my wife's home, she had a tower about 3 meters high. It seemed to have enough pressure for the house but when I installed a shower heater, there wasn't enough pressure to make the pressure switch in the heater. Since I had to buy a pump anyways, the tower was eliminated. I now have an 1,800 liter storage tank with the pump.

 

It's entirely possible that some shower heaters will work with lower pressure. Mine wouldn't.