New Loft Conversion and Water Pressure

[Chris1012]

We’re having a loft conversion done in a few weeks. We’re concerned about the pressure that we will have in the loft bathroom when other showers in the house are in use (we will have 3 showers and would like them to be able to be used simultaneously).

We have been looking into unvented cylinders as an option. Our incoming water pressure at present is 3 bar and we have a combi boiler which currently works well. Our understanding of the unvented cylinders is that they can be run via a boiler (indirect) or independently with an immersion (direct).

In order to minimise disruption we are wondering whether is it feasible to run a pipe off the mains up to loft and heat an unvented cylinder directly to supply only the loft bathroom, keeping the rest of the house on the combi boiler. (The pipe would be able to run straight up in the wall to the loft from the mains entry in the cellar. If it were to go via the boiler then we would have to lift some of the kitchen floor and possibly disrupt flooring in the bedroom/bathroom above).

We also have a water softener under the kitchen sink that runs through the boiler and services all the current bathrooms (2) and rads.

I hope this makes sense!

 

[daWilko]

Hi - it's good you've got 3 bar, but you might struggle to get good service from 3 showers at once. What happens now if you've got two showers running and the bath filler is opened ?

 

[Chris1012]

Hi - it's good you've got 3 bar, but you might struggle to get good service from 3 showers at once. What happens now if you've got two showers running and the bath filler is opened ?

Thank you for responding.
If both showers and bath are in use, the flow rate is at very minimal rate.
Two showers can run simultaneously and two people can shower separately however the flow rate is literally just about enough.
As we are going even high with the plumbing, I assume the loss of flow rate will be even worse in the loft.

 

[townfanjon]

As above , no chance 3 at the same time , well not half decent ones lol .
Unvented cylinders are all about pressure and flow , the two need measuring and at times of high demand . You need a dynamic water pressure taking not standing. Dont for get your water pressure diminishes by 0.1 bar every meter higher you go .
Get a qualified G3 guy round to advise you .

 

[Chris1012]

Right had a further think about this -

The loft bathroom will be used for occasionally for guests for now and in the future most probably for two of our children.

If we go for an unvented indirect cylinder setup, we would have to cause some considerable damage to our current kitchen flooring and hallway, for the pipes to get to our current combi (33kw), main supply pipe, water softener (under kitchen sink that supplies softened water to all bathrooms and boiler) and then up to the loft.

However if we went for a small direct unvented cylinder to supply the loft bathroom only, we would not need to disrupt the kitchen and could t-off the mains supply in the cellar and run the one 22mm cold feed straight up in the wall to the direct unvented cylinder in the loft. We would have to purchase a separate water softener for the loft but this setup would be for the one bathroom only.

From my understanding the cost of running a direct unvented cylinder is considerably more expensive than an indirect one, however as it will be supplying just the one bathroom, we are thinking this may be the best route to avoid the big disruption if we went for the indirect setup.

Just wanted to ask you all what your thoughts were on the above, if my understanding is correct and if there is any other better way of achieving our required setup?

 

[daWilko]

Another possibility is an electric instant HW service for the loft only. This needs a substantial cable (and a cold water feed) but has the advantage of no energy used to keep it warm in idle periods.

 

[justlead1]

Pushing mains water through a combi create a lot of frictional resistance reducing flow on downstream side, so using the 22 mm straight up to loft may be good but water softeners also restrict flow. You could experiment, run pipe up there with a valve on the end and try it with showers running. (Discharging without flooding building.)

 

[Jim Goodenough]

You can get high flow rate water softeners nowadays - just check out the spec before buying.