Advice on Unvented Cyclinder not enough for 2 showers

[marc1977]

Hi,

I have a Bosch unvented cyclinder (fitted last year) and it works great but only has enough pressure to run one good shower at a time. The shower pressure also drops when the toilet is flushed. We have good water pressure to our house and i believe the cylinder PRV has been set to around 3 bar. Ive noticed we do only have a 15mm mains pipe feed the house although the plumber has used 22mm pipe where he could to feed the Mains water into the cylinder.

The only thing i can think of trying is to increase the pressure by adjusting the PRV however as this is already at a good pressure (its certainly at least 2 bar judging by the shower pressure we get when run on its own) im not sure this will help. Any advice?

Thanks

Marc

 

[Scott_D]

You need to check your incoming flow and pressure
Make sure the internal and external stop tap is fully open
Have the cylinder serviced and check any strainers are clear

 

[Chuck]

We need a few more details, please. What do you mean by a 'good shower'? (How many litre per minute and for how long?) What is the size of your unvented tank?

 

[marc1977]

We need a few more details, please. What do you mean by a 'good shower'? (How many litre per minute and for how long?) What is the size of your unvented tank?

Hi,

Im not sure of the tank size but its huge and definitely has enough water in it. The issue happens right away so its not an issue with the size of the tank.

By a "good shower" i mean we used to have a 3 bar shower pump before the unvented cylinder. the shower seems to have a similar amount of power now so is absolutely fine on its own. However if you put 2 showers on the pressure significantly drops in both showers.

 

[Chuck]

By a "good shower" i mean we used to have a 3 bar shower pump before the unvented cylinder. the shower seems to have a similar amount of power now so is absolutely fine on its own. However if you put 2 showers on the pressure significantly drops in both showers.

Please describe the pipework that goes from the cylinder to the showers. What diameter (e.g. 15mm / 22mm / 28mm) and length is the section that will be 'shared' when both showers are operating? A couple of photos would be helpful.

And please answer the question about how much FLOW in litres per minute gives you a good shower when just one is operating. Measure this by timing how long it takes to fill a container, such as a jug, of known size.

 

[ShaunCorbs]

What’s your incoming pressure and mains cold water ?

pressure ?
Pressure with another outlet open ?
Flow ?
Flow with another outlet open ?