Shower pump selection

[Serval]

I planning on fitting a shower pump and shower valve diverter on my shower room refurb.
I have a gravity fed system (CW from a loft tank and HW from the cylinder)
Previously had an aqualisa digital.

Have done a bit of research and looked on the stuart turner app for different pump selections.

The bit im not sure about is how to work out my head pressure in order to determine if i need a universal, positive or negative pressure pump.....
Ive seen a few vids online where people time how long it takes to get one litre of water from the shower head.

Ive already disconnected my shower head and only have the aqualisa digital unit that needs to be disconnected come out.

Once ive disconnected everything
Can i just measure the output rate from the open outlets for the CW or HW

Im thinking that by not having the shower head attached and also the pipe outlet being at a lower level than where the shower head would result in a higher flow rate so im unsure if this is an accurate way of checking the head pressure.

Any advice appreciated

 

[SimonG]

Its height of shower head to base of cold water tank you need to measure.

 

[Serval]

Its height of shower head to base of cold water tank you need to measure.

is that it, Or is there a calculation or formula i need to plug that measurement into to work out the actual head pressure?

 

[Ben-gee]

That is it for these purposes; there will be frictional losses is pipework and elbows etc but for your purpose a simple height calculation will suffice.

For your information, the terms ‘universal’ and ‘negative head’ are interchangeable in this context.
The trend is to use the term universal, as this pump will work in all situations.

The positive head pump is cheaper to buy and has less to go wrong - so I always use this where possible.

Others I know just use a universal pump in all cases as it will always work - lazy? risk averse?

If you are borderline on the specs then go for a universal.

Personally recommend ST Monsoon if you can afford it, they are really good.

 

[rpm]

What Simon said determines what sort of pump you need then you select 1.5, 2 or a 3bar pump for required pressure depending on how you like your showers.

 

[Serval]

Thanks all for the info and recommendations.

@Ben-gee
Initially I was thinking to just go for a universal as that would cover me for all cases but now i know a bit more i can do enough to to see if i can use a positive which should hopefully be more reliable

 

[rpm]

That is it for these purposes; there will be frictional losses is pipework and elbows etc but for your purpose a simple height calculation will suffice.

For your information, the terms ‘universal’ and ‘negative head’ are interchangeable in this context.
The trend is to use the term universal, as this pump will work in all situations.

The positive head pump is cheaper to buy and has less to go wrong - so I always use this where possible.

Others I know just use a universal pump in all cases as it will always work - lazy? risk averse?

If you are borderline on the specs then go for a universal.

Personally recommend ST Monsoon if you can afford it, they are really good.

Less to go wrong??

 

[Serval]

Less to go wrong??

I took that to mean they are more reliable. But i guess you guys with more experience have a good idea of if thats the case or not

 

[exedon2]

If your going to fit a S T monsoon I would not worry too much. Ultra reliable even in the area I live in with water that's described as 'very aggressive'
I've a fair number ive fitted well over 10 year old still going , my own 4.5 hot water boost pump is 15 + years and has never been touched.

 

[Ben-gee]

Less to go wrong??

A ‘universal’ has an additional pressure vessel, this can lose pressure or fail completely- so something else to go wrong.

 

[rpm]

A ‘universal’ has an additional pressure vessel, this can lose pressure or fail completely- so something else to go wrong.

All true however vessel can be repressurised or replaced if needed and the ST has a decent warranty period so all is not lost.

 

[Ben-gee]

No, I agree they are an excellent unit.

I just don’t like it when people fit them unnecessarily, where a positive pump would work.