22mm or 15mm to a bath

PCW · Nov 22, 2019

I have run 22mm plastic to three showers and 22mm copper to the bath. Intention was to run 22 all the way to below the bath with last bit in 15 as normal.
The bath manufacturer now says they can't put the taps where we want. I don't want to chase in 22mm pipe into the wall (too deep). I could reduce to 15mm and chase them in but that would mean an extra 2 meters of 15mm pipe. Question is would this make that much difference in flow real terms.
I wouldn't mind if the hot came straight from a tank or boiler as then bath filling would be with hot and cold so both almost full on. We have the hot coming out of a thermal store so at about 50 degrees meaning there would not be much cold needed. I'd like to know if that would effect the time to fill a bath?
Many Thanks
The bath maow

nufactureer

Brambles · Nov 22, 2019

That can only be determined if you know the rate of flow from the thermal store. Therafter, you can calculate the impact of replacing 2m of 22mm with 15mm.

I would aim to design for a bath to be filled for use in 5 to 7 minutes.

In simple terms, a 15mm pipe has half the flow rate of a 22mm. Be aware that If you have a high flow rate from the Store and you reduce to 15mm, the velocity will increase which increases the level of noise in the pipework.

If in doubt use 22mm

PCW · Nov 22, 2019

Brambles said:
That can only be determined if you know the rate of flow from the thermal store. Therafter, you can calculate the impact of replacing 2m of 22mm with 15mm.

I would aim to design for a bath to be filled for use in 5 to 7 minutes.

In simple terms, a 15mm pipe has half the flow rate of a 22mm. Be aware that If you have a high flow rate from the Store and you reduce to 15mm, the velocity will increase which increases the level of noise in the pipework.

If in doubt use 22mm

Many Thanks, 5 to 7 minutes to fill a bath... that is the figure I was after.

The store heats a coil for DHW so flow is whatever the cold is. The outside tap flow is very good and that's on the end of about 4m of 15mm so I think I'm over thinking this. I'm going to time filling container from the outside tap.

Trouble is you don't know what you don't know so thanks for your comments.