Bore size for a shower hose with a Fully pumped supply

[Reddwarf4ever]

this may sound a basic question, but it is important. I have seen so many conflicting opinions, even from manufacturers. Some say, just use the biggest bore possible, others say use a small bore 8mm for a fully pumped system & a large bore 11mm for a gravity system. There must be a reason why different size bore hoses are manufactured.

I changed the shower hose yesterday, thinking it to be the same; although it did have a scale catcher fitted, which I discarded, to a full bore 11mm shower hose, but it appears the flow is now less, so should I change it to an 8mm bore to achieve the maximum flow rate.

Many thanks

 

[ShaunCorbs]

I suspect you mean the pressure is different as the flow rate will be more with the 11mm aslong as the shower matches

 

[Reddwarf4ever]

I suspect you mean the pressure is different as the flow rate will be more with the 11mm aslong as the shower matches

I said flow as the shower water wasn’t as good, maybe I am referring to pressure coming from the shower head 🤔 so in that case would an 8mm bore hose give me more pressure at the shower head ?the previous hose was, I believe a full bore also, but was 1.25m whereas this hose is 1.5m......so am I best replacing with an 8mm bore or 11mm bore 1.25m hose ?

 

[steadyon]

If its an electric shower, best to match the old and new hose bores.

 

[John.g]

A bigger bore hose always IMO but for a electric shower won't make a huge difference as its limited thermally to 3.5/5 LPM.
If you had a 1.5M 11mm hose the pressure drop will be 1.88M at 20 LPM, a 1.5M 8mm hose will have a pressure drop of 8.88M for the same flow rate of 20 LPM or almost 5 times greater but the shower head is most important, a electric shower with a flow rate of 4 LPM with its proper head can feel more pleasant than a shower with the improper head (jet size) at 8 LPM.

 

[Reddwarf4ever]

A bigger bore hose always IMO but for a electric shower won't make a huge difference as its limited thermally to 3.5/5 LPM.
If you had a 1.5M 11mm hose the pressure drop will be 1.88M at 20 LPM, a 1.5M 8mm hose will have a pressure drop of 8.88M for the same flow rate of 20 LPM or almost 5 times greater but the shower head is most important, a electric shower with a flow rate of 4 LPM with its proper head can feel more pleasant than a shower with the improper head (jet size) at 8 LPM.

Hello
so that means basically, there is no point in considering an 8mm bore hose, even though I have a dual pumped water supply from an immersion cylinder, . internet searches vary enormously one manufacturer said an 8 mm bore will increase the flow a lot, Others say the bigger the better. It’s not just about flow, I assume the pressure at the shower head is also a factor ( thinking of jet wash machines, not much water but a lot of pressure )

so how much difference would a 1.25m vs a 1.5m 11mm bore hose be ?.....thanks

 

[John.g]

In the example I gave above, 1.88M drop @ 20LPM in a 1.5M 11mm hose becomes 1.56M drop @ 20LPM in a 1.25M 11M hose so theoretically for the same dynamic head before the hose to give 1.88 drop you should get ~ 22LPM but in practice you will see little or no gain as the increased pressure loss in the shower head and the slight drop in your pump head will mean a very small increase in flow, the total head loss from the pump discharge(s) to the shower head must be used when calculating flow rates.