loft shower water pressure and combi boiler

zerog

We bought a property which we are renovating before moving in. We viewed the property in March and the heating and showers were working fine.

It is a terrace with 3 floors including a loft conversion.

When we tried turning on the heating in November it didn't work. The boiler is 15 years old so rather than pay a quoted £500 for repair we will get a new one.



A plumber has quoted for a new Valiant Ecotec 832 and is also offering the 835, which will be installed in an outhouse attached to the kitchen wall on the ground floor (where the current boiler is).

Our builder seems to think that even the 835 will not provide sufficient water pressure to the top floor shower. But he also said that the current shower has a pump.

The plumber said that was rubbish as you can't have shower pumps with combi boilers. Google agrees with this, but the builder has done a good job with the kitchen refitting so far, so not sure why he has got this wrong?? Is there such thing as a cold water only pump?



Anyway, the plumber turned on the top floor basin tap and said the cold water mains pressure was pretty good. He thinks the 832 would likely suffice, but he can't be sure about the shower water pressure as the hot water is currently not working.

There are 2 bathrooms on the top and middle floor, kitchen sink and washing machine on ground. I guess it's unlikely that both showers would be in use at the same time, but potentially the washing machine might be on when someone is showering.

We intend to replace the top floor shower with this model: https://www.grohe.co.uk/en_gb/grohtherm-1000-thermostatic-shower-mixer-1-2-34438003.html


The 832 has a flow rate of 13l/min and the 835 is 14.3l/min. Any comments, are we even considering the right factors?

nofoollikeold

1. The water pressure supplied will be that of the incoming cold water main.
2. Before installing a combi boiler, make sure the incoming cold water pressure and flow rate are adequate.
3. The shower you want requires a minimum of 1 bar pressure. The loft will be approximately 5 metres above the ground, which height will "lose" you about 0.5 bar. So you'd need an incoming pressure of at least 1.5 bar.
4. The shower flow rate would be about 14 litres / minute at 3 bar, less at 1 bar. So you'd need a mains flow rate of, say, 12 litres per minute minimum, and preferably a good deal more.
5. You might consider making one of the showers an electric one, run off the incoming mains. This would give you a source of hot water while any fault with the boiler was corrected.

DorsetLad

I would say you are not considering all the relevant factors. Firstly, if the heating is not working, do you know it is the boiler that is at fault, rather than say a pump (if it is a gravity-fed system)?

It would help to know what type of system you have at present (combi, or system boiler with un/vented hot water cylinder?). If your present boiler is a combi, then the water pressure in both the hot and cold taps is set by the mains pressure, so the model of boiler you choose is not relevant to the question about water pressure. How good is your mains pressure? How good is the flow from taps in in the loft conversion when both are turned on (even if the hot water is not getting hot) – would the flow be enough for a shower?

In my opinion a combi would not be ideal for your situation. For 2 bathrooms and a kitchen sink (which could easily be turned on when someone is showering), I would have though a system boiler with unvented cylinder would be a better solution. This is what we had installed recently and we love it: lots of hot water under mains pressure, irrespective of how many taps are turned on.

Judging by the various comments of the builder and the plumber, I would suggest you get some quotes from gas-registered central heating people who know what they are doing, who can measure both water pressure and flow, and who can assess your current and future needs and advise accordingly.

(Disclaimer: I am not a central heating engineer but I did read up a lot about CH systems before we chose ours!).

southcoastrgi

DorsetLad wrote: »

(Disclaimer: I am not a central heating engineer but I did read up a lot about CH systems before we chose ours!).

I would say you are talking a lot more sense than both the OP's builder & plumber.