Low Water Pressure

[FRAN1870]

Hello all,

We have two electric showers in the house but can't run them simultaneously because the water pressure drops and the unit flashes blue and they run cold (assume safety feature). Both are find when running independently but the same happens when we flush the toilet or turn other taps on.

We live on top of a huge hill and the water supply is also shared with the house next door (both houses used to be one big house). I've done a simple flow rate check and get just over 10L per minute.

Is there anything I can do to my system such as accumulator tanks etc to balance the pressure and stop the pressure dropping when both showers are used?

Thanks in advance,

Fran

 

[endecotp]

Is your electricity supply really sufficient for two electric showers at the same time?

You already know about accumulators. The other factor is pipe diameter, both within the house and in the supply to the house.

IIRC, regs limit the extent to which shower pumps can suck water in from the mains so that you don’t cause problems for your neighbours.

You should get some answers from experts soon; I have no personal experience with any of this.

 

[FRAN1870]

Thanks, Yes I know there are many factors.... The electrician who installed the cable didn't have any concerns about the additional load?
They are 8.5KW and both on their own feed back to the main board run with 10mm twin & earth, if memory serves they are on 32amp (will check with the sparky).

I'm also no expert but anything pulling more than that would trip the main board?... I think the whole system is fused to 60amps?

 

[endecotp]

You might like to ask in “electrics” about that; if it really is a 60A main fuse I think you’ll probably get away with it in practice as long as you don’t also have electric heating.

 

[JohnD]

the number on the fuseholder cover may not be the same as the rating of the fuse inside it.

It is a bit more likely to be right if it is a paper one that's quite new and has never been cut open.

If you run two electric showers at the same time there is a risk of overload or overheating, or of voltage drop, especially if you are in the country or an old house.

8.5kW is about 37 Amps
Each.

With electric showers I deduce that you have no gas supply so you have an electric cooker and heaters.

 

[FRAN1870]

They are on 40amp ... we’ve not run them simultaneously so I think I need to get this assessed again before looking at the water pressure.

The one shower has provision to easily change to a mixer / power shower but I need to get the cold water tank lifted higher to improve the pressure on that first

Old houses

 

[Dan Robinson]

Is there anything I can do to my system such as accumulator tanks

Yes, depending on budget and space constraints

 

[dilalio]

Yes, depending on budget and space constraints

Indeed

N.B. Megaflo was existing!

 

[FRAN1870]

Indeed

Crikey what's that lot?

 

[FRAN1870]

Had a plumber out and he's telling me to pressurise the hot feed using an unvented cylinder.
Then I can run hot/cold to the shower in the ensuite and leave the shower in the family bathroom on the cold feed only (electric shower until we refurb that again).

Thermostatically won't the hot / cold mix to the ensuite shower still depend on the mains cold pressure? Won't the shower still go hot if the toilet flushes?

 

[endecotp]

Sounds like nonsense, if your description in the first post is correct.
(I suppose it will not actually cut out, in the way that the current electric shower does, but it will still lose flow rate when other taps are open.)

 

[endecotp]

The big black cylinder is an accumulator.

 

[FRAN1870]

Sounds like i’d still need to have an accumulator on the cold whatever then, the unvented cylinder will only increase the hot water pressure which frankly isn’t really giving us any problems. It could be a little quicker running a bath but no biggy.

Doing what he said could actually be dangerous if the pressure drops... it could scald the kids!

The other option I’ve read myself is a break tank with a pump? I’ve seen a few all in one systems that boost flow rate. Assuming I could get one big enough to handle demand, then would the better flowrate solve fluctuations? or will the shower still go cold when I flush the bog whatever?

 

[Dan Robinson]

The accumulator will increase the flow to both and the work in general will equalise the pressures.

 

[endecotp]

the unvented cylinder will only increase the hot water pressure

With an unvented cylinder, the hot water pressure and the cold water pressure will be essentially equal; your hot water pressure will drop when you flush the loo etc.