Can anybody tell me what determines the whether or not a secondary return is required on a unvented cylinder?

The reason i ask is that a friend has a small hairdressers and has got a Ariston 210 litre cylinder and he feels the hot water flow rate is quite poor. I suggested putting a pump to the hot water but that means a new hot water supply is required on the return. Is this correct.
Any info would be grateful
cheers

Not sure I quite understand you, but I have unvented cert citb reg 01939173/1

First thing to try is to run a new 25mm mdpe blue water pipe from the boundary of the property. It can actually be aranged to get the local water supplier to provide a new connection from the main pipe in the centre of the road so you have a much better flow rate.

In the dwelling use 22mm pipe everywhere.

If you still don't get an adequate flow, then likely the water company isn't able to supply your needs. This is not unusual in some localised areas. All that is required of them by law is that water comes out of your tap, not at any particular rate.

In such cases then the only solution is to store your own water and pump it. That is how you have to use a pump in unvented scenario.

Hope that helped.

Paul

pauliepie wrote:
Can anybody tell me what determines the whether or not a secondary
return is required on a unvented cylinder?

.....means a new hot water supply is required on the return. Is this
correct.

No. If it's a new problem but an old installation, then I'd suggest you
get the inlet strainer cleaned, they scale up. The system should be
serviced annually. There's also strainers on some outlets and on
thermostatic mixing valves which can also get clogged & restrict the
flow.

The secondary return simply circulates hot water around the pipework
installation, so you don't waste water and time by running off a few
gallons of water before you get hot water from the tap.

Thanks for that guys, its just that i assumed if the hot water run was more than about 12m in length then a secondary pump on the hot water return is needed which i read off the internet somewhere.
So in general, the pressure that comes into the cylinder determines the pressure on the outlet side?

cheers for your help

The reason i ask is that a friend has a small hairdressers and has got
a Ariston 210 litre cylinder and he feels the hot water flow rate is
quite poor. I suggested putting a pump to the hot water but that means
a new hot water supply is required on the return. Is this correct.
Any info would be grateful

You are getting confused. You appear to be thinking of a pumped return
circuit, which is used to keep the water in the pipework hot so that the hot
tap gives hot water immediately. It will have no effect whatsoever on flow
rate, although might be useful if there are large runs of pipework,
particularly in a commercial setting.

If the flow rate is poor, it is because something is blocking the water.
Possible culprits:

1. Valves not fully open. (Open them.)
2. Pipework/valves scaled up/seized. (Descale or replace them.)
3. Pipework undersized. (Replace it)
4. Mains supply in street inadequete (Fit large accumulator or use tank and
pump).

Has it ever worked well?

Christian.