Hi,

We are having a new bathroom and en-suite re-fitted.
We have gravity fed system.

For the ensuite we are thinking of having a shower and body jet column
which requires 2 bar min.

For the bathroom we are thinking of having the Aqualisa Quartz pumped
shower with a fixed head and a shower handset.

Our water company has said that the incoming water pressure is 1 to 1.5
bar min.

I was wondering if it would be possible to run a separate 2 or 3 bar
pump, Stuart Turner Monsoon, for the shower and body jet column in our
ensuite as it backs onto the airing cupboard where the HWC is and place
it on the floor or site it try to have it sited in the loft using a
negative head pump as it would be directly over the ensuite but below
the cold water tank in the loft.

For the bathroom I was thinking of placing the Aqualisa Quartz pump
under the bath as that would service the fixed 6in shower head and
separate shower handset, which would a have a diverter to switch
between the 2 and seems straightfoward.

The Aqualisa pump is rated at delivering 13Litres a minute or 18 Litres
if boosted @ 0.1 bar.

The Stuart Turner Monsoon pump for the ensuite is rated has having a
max. flow rate of 25litres.

I would just like to know if using two independant pumps to service two
areas would be OK or would it pose problems.

The salesperson at my local bathstore said that it might cause
backsiphonage problems and drain the water supply very quickly if both
are used at the same time.

Any advice would be greatly welcomed.

On 1 Jan 2006 01:57:43 -0800, wrote:

Hi,

We are having a new bathroom and en-suite re-fitted.
We have gravity fed system.

For the ensuite we are thinking of having a shower and body jet column
which requires 2 bar min.

For the bathroom we are thinking of having the Aqualisa Quartz pumped
shower with a fixed head and a shower handset.

Our water company has said that the incoming water pressure is 1 to 1.5
bar min.


That's not really very meaningful. First of all, what actually
matters is the flow of water into the house. Measure that at the
kitchen cold tap by timing how long it takes to fill a container of
known size. Secondly, measure the rate that the cold tank in the
roof fills. This can be done by first turning off the water to it
then emptying a known volume out (e.g. N bucketfuls from the bath
tap.) You'll need several for this. Then turn on the supply to the
tank and time how long it takes to refill.


The point of doing these tests is to check that you have enough cold
water storage capacity and the ability to refill it. When you add
these showers, if you run them both at the same time, you can easily
be using 30 litres per minute. This doesn't mean that you have to
necessarily be refilling it at that rate, but you do need to do the
sums. If it's only refilling at 10 litres/min, then in my example,
you are using water at a net rate of 20 lpm, so for example a 200
litre tank would empty in 10 mins. This may not please your wife if
the shower stops that quickly.

The reason for measuring the kitchen flow rate from the main is that
it is typical for the supply from there to the tank to be in 15mm
tube. If you find that you have good flow at the kitchen, then you
could upgrade the pipe to the loft and fit a larger float valve or
even two float valves to improve the capacity.

Either way, you may need to consider adding tank capacity, perhaps by
adding a second tank and connecting the two.

The other issue to consider is whether your hot water storage is
sufficient. Again because the flow is increased, you will be going
through hot water faster than before.

For this you need to use a formula to calculate the hot water required
to produce a certain amount of warm water at shower temperature.

Using


Vc[Tf-Tc] = Vh[Th-Tf]


where


Vc = cold volume
Vh = hot volume
Tf = mixed water temperature
Th = hot temperature
Tc = cold temperature


If you take a worst case of wanting both showers to run simultaneously
for 20 mins - that would be 600 litres of warm at 40 degrees.
Consider cold temperature to be 8 degrees in the winter and hot water
storage to be at 60 degrees.

This gives

Vc[40-8] = Vh[60-40]

We know that Vc = Vf -Vh so

[600 - Vh] * 32 = 20 Vh

19200 - 32Vh = 20Vh

52Vh = 19200

Vh = 369 litres.


Of course this is an extreme example.

First of all it ignores the fact that the boiler will be replenishing
the cylinder with heat almost as soon as you start running the shower.
However, if the boiler to cylinder circuit is "gravity" i.e. has large
pipes to e.g. a back boiler (boiler has two pipes for HW and two for
CH) then the rate of reheat may only be around 5kW. A system that is
fully pumped may only be reheating at 10 perhaps 15kW if you're lucky.
Modern cylinders can achieve 20kW or even more if a fast recovery
type.

You can calculate the amount of heat needed to heat the water in the
cylinder using the formula

Energy = mass x specific heat x temperature rise

For water measured in kg (approx litres), the specific heat is 4200
J/kg.C


Let's say that you can heat the water at a rate of 15kW and the
required temperature increase is from 8 to 60 degrees (using the above
numbers).

15000 = volume/sec x 4200 x 52

vol/min = (15000 x 60) / (4200 x 52)

Just over 4 litres/min, or in 20 minutes of running, 80 litres.


So.....

The implication of all of the above would mean that you would need a
290 litre cylinder !!!


However, these are worst case scenarios. You can plug in different
numbers and see what you get.

However.....

- a typical existing domestic cylinder is usually only 80-120 litres

- it may well only be heating at the rate I've illustrated.

- you might not be using water at 40 lpm - especially if both showers
are not used simultaneously for 20 mins and one only uses 15lpm.


The point was that it is important to look at both the hot and cold
capacities before you start.

If you are going to have to replace the cylinder, You might want to
rethink the whole thing and go for a pressurised cylinder or a
heatbank *provided that* the cold mains are up to supplying the total
flow rate required. The cost of that would not be significantly
different than a replacement standard cylinder plus two pumps.



I was wondering if it would be possible to run a separate 2 or 3 bar
pump, Stuart Turner Monsoon, for the shower and body jet column in our
ensuite as it backs onto the airing cupboard where the HWC is and place
it on the floor or site it try to have it sited in the loft using a
negative head pump as it would be directly over the ensuite but below
the cold water tank in the loft.

Floor level is recommended by manufacturers over a loft installation.




For the bathroom I was thinking of placing the Aqualisa Quartz pump
under the bath as that would service the fixed 6in shower head and
separate shower handset, which would a have a diverter to switch
between the 2 and seems straightfoward.

The Aqualisa pump is rated at delivering 13Litres a minute or 18 Litres
if boosted @ 0.1 bar.

The Stuart Turner Monsoon pump for the ensuite is rated has having a
max. flow rate of 25litres.

I would just like to know if using two independant pumps to service two
areas would be OK or would it pose problems.

It's a better idea to have two.





The salesperson at my local bathstore said that it might cause
backsiphonage problems and drain the water supply very quickly if both
are used at the same time.

Hmm....

Well now you understand the point about total use.....





--

..andy