Water pressure - electric shower or water pump?

[Chuck]

Keep in mind that heating water by electricity is a lot more expensive (at least historically) per litre than using gas. Last time I estimated this for a 8.5kW 10 minute shower it was 73p vs 40p assuming the flow rates were equal. So, with two people each taking a daily 10 minute shower the electric option cost £241 / year more to run.

Please check my figures, the above are from memory and YMMV.

 

[JohnMalcolm]

Keep in mind that heating water by electricity is a lot more expensive (at least historically) per litre than using gas. Last time I estimated this for a 8.5kW 10 minute shower it was 73p vs 40p assuming the flow rates were equal. So, with two people each taking a daily 10 minute shower the electric option cost £241 / year more to run.

Please check my figures, the above are from memory and YMMV.

This is what I thought that these electric showers are not cheap to run.
In this case my question is installing a pump for the whole system less disruptive than dedicated shower booster pump?
If less then I go for a pump for the whole system.

 

[John.g]

Are you considering just boosting the hot water pressure?.

Electric/gas, a 9kw electric shower will give a average of ~ 4.2LPM at 40C, you might expect 3 times that with a pumped (gas) pumped shower, so the running costs of both per unit showering time is pretty similar based on energy costs here anyway. Of course you must be happy with the low electric flowrate.
Running cost of a 9kw electric shower is 0.15xcost/kwh pence (per minute), if you are paying say 45p/kwh then the running cost is, 0.15x45, 6.75p/minute or 34p for a 5 min shower.

 

[JohnMalcolm]

Are you considering just boosting the hot water pressure?.

Electric/gas, a 9kw electric shower will give a average of ~ 4.2LPM at 40C, you might expect 3 times that with a pumped (gas) pumped shower, so the running costs of both per unit showering time is pretty similar based on energy costs here anyway. Of course you must be happy with the low electric flowrate.
Running cost of a 9kw electric shower is 0.15xcost/kwh pence (per minute), if you are paying say 45p/kwh then the running cost is, 0.15x45, 6.75p/minute or 34p for a 5 min shower.

Yes just boosting the hot water, cold has very good pressure: 3.75

 

[Ric2013]

Re. the pull cord switch, this is usually because it is the only type of switch allowed near the shower. Realistically, you could probably put a 45A wall switch just outside the bathroom and it would serve the same purpose.

 

[JohnMalcolm]

So how do you reckon should I install the pump or the electric shower?

 

[JohnMalcolm]

I asked the plumber and booster pump for the shower only or a water pump for the whole system does not make much difference in terms of additional pipe work so electric shower still wins in terms of labor.

 

[John.g]

You said in your first post the the pressure in your upstairs bathroom is a bit weak, imo you need at least 2.5 to 3 bar static pressure downstairs to give you 5.5LPM or so in the summer at the 1Bar dy.namic minimum required by a 9.5kw shower in the summer, otherwise you may have to switch to 1/2 power which isnt much fun. You can buy a electric pumped shower where the pump is integral with the shower but this requires a gravity supply from a CWST in the attic.
You can install a PRV on the mains set to ~ 0.5bar to a pumped shower but I think it invalidates the warranty, I did it for a friend years ago and the shower is running away fine.

 

[JohnMalcolm]

You said in your first post the the pressure in your upstairs bathroom is a bit weak, imo you need at least 2.5 to 3 bar static pressure downstairs to give you 5.5LPM or so in the summer at the 1Bar dy.namic minimum required by a 9.5kw shower in the summer, otherwise you may have to switch to 1/2 power which isnt much fun. You can buy a electric pumped shower where the pump is integral with the shower but this requires a gravity supply from a CWST in the attic.
You can install a PRV on the mains set to ~ 0.5bar to a pumped shower but I think it invalidates the warranty, I did it for a friend years ago and the shower is running away fine.

right, the cold water pressure downstairs (ground floor) is 3.75

 

[John.g]

3.75 bar shoud be fine for a mains supplied electric shower installed upstairs.