Reverse Circulation when HW On

[Daveydub]

There are a few different ways to put the pipework in order.
1 check valve is fitted and it requires 2 further one to overcome the system flaws.
We still have no answer to my last question re the noise problem

 

[fixitflav]

1 check valve is fitted and it requires 2 further one to overcome the system flaws.

Depends on the number of upstairs rads and how they're connected to the return header.

Edit
If the cylinder return pipe is rerouted there's still a problem of teeing in at the boiler, very awkward from pic in #26. Maybe easier to tee in between the Spirotrap and the pump boiler return connection.

.

 

[Daveydub]

1 check valve is fitted and it requires 2 further one to overcome the system flaws.

Edit, I notice how badly worded that was.

1 check valve is fitted and it requires 2.
1 more to overcome the system flaws.

Depends on the number of upstairs rads and how they're connected to the return header.

Doesn't matter how many and they are shown as connected in with one tee.

Cylinder return would need to tee in between tee 3 and boiler but it may be simpler to take downstairs flow to airing cupboard and fit a zone valve to it. This has advantage of providing separate control over up/down heating.
All depends on house and pipework layout.

 

[fixitflav]

Doesn't matter how many and they are shown as connected in with one tee.

Sketch in #5 shows one block representing all upstairs rads. If the returns are all commoned before joining the main return pipe one check valve in the common pipe needed. If they're all separate it needs a check valve for each (we don't know how many upstairs rads).

Cylinder return would need to tee in between tee 3 and boiler

Yes, but it could be up or downstream of the Spirotrap.

All depends on house and pipework layout.

Exactly