DIY plumbing our extension

[JamSte]

Hi all, 

 

We’ve recently had our plans approved for our extension and am looking at areas that we can do ourselves. Appreciate that the boiler etc needs to be completed by a gas safe engineer but thought doing the pipes for a lot of the plumbing could save us some money. 
 

We will have 3 bathrooms, 2 on the first floor and one in the loft. The loft bathroom will have a double shower fitted to it and a bath. 
 

looking at unvented cylinders I’ve looked at the Dutypoint cylinders and have been told I’d need 700l tank. This has a 28mm output. Am I best in taking a 28mm pipe from the ground floor plant room and then teeing off to each bathroom in 22mm for the bath then 15mm for the showers. 
 

run to the first bathroom would be approx 8m. The second bathroom back on to this and would be a further 4m from this. The third bathroom sits above the first and is probably a further 6-7m. So total on that run probably 15m.  
 

there is a chance that all 4 showers could be run at the same time in the mornings. 
 

We will be having a break tank fitted 800l with a 4 bar pump. 
 

with the pipe size we are looking at and the length of the runs are we best to install a secondary return too. Or should it not take too long to get hot water to the taps upstairs in the loft. 
 

thanks in advance for the help

[ProDave]

I have never heard of anyone needing a 700L hot water tank.  I would be questioning whoever specified that.  How are you heating the hot water?

[JamSte]

It will be heated by standard boiler. I take it the tank is bigger than needed. It was quoted by a plumber that came out recently and said that because all of the showers could be used at the same time and there being 5 of us in the house it needed to be big. I’m guessing this isn’t the case?