Increasing water pressure options

[Madrab]

Not at all @Josh1987 , that's why we are all here, to help if and where we can.

You're correct though, if you were running 2 showers at once, through a decent sized dual pump, you could easily run a 50 gal (220l) cistern dry in no time, especially if the supply can't replace the volume being used at the same rate. You would also need to ensure the Hot Water cylinder can supply an adequate amount of hot water to run those same 2 showers and anything else that mind be used at the same time. That and the cost to install the whole system properly will be pretty expensive.

I think you need to look at your mains supply first of all and see what that can do for you before deciding what direction to go in.

You need to do the test at the outside tap first (if that has the highest apparent flow), see what pressure and flow that can deliver, whilst another outlet is open, that will give us your dynamic mains supply pressure and flow and allow more educated advice to be offered.

 

[oldbuffer]

1. As Madrab says, and as pointed out in post #7, you would need to pump hot and cold for a stored water solution, unless you went for the unvented option.
2. It would be best to avoid pumping any but the showers. Pumps rely on the water passing through them for lubrication. For a shower, you normally have hot and cold running at the same time, so a twin pump has water in both sides. For baths / basins / bidets you often have only hot OR cold running, which would leave one side of a twin pump dry. You could pump the supplies separately, or use a "whole house" pump.
3. You would need to revise the pipework to pump or pumps. A twin pump requires a dedicated feed from the CWSC and a dedicated feed from the HWC. Also, for the HWC, you would probably need to fit a special flange for the hot water off-take for the pump to avoid air in the supply.
4. If you are able to go for an unvented cylinder, you have only one storage cylinder, and no pumps. However, you might be advised to have one shower as an electric shower, so that you have a source of hot water in the event of a boiler failure.

With respect to "what works best" its largely a matter of personal choice:

My preference is for a vented HWC with loft CWSC. You have a store of water available even if the water supply is off. The pump is slightly noisy, but get a good one and install it properly and they last a long time. My Stuart Turner has been in daily use for the last 33 years, but it is an expensive one with bronze pump housing. I regard it as a fit and forget solution.

The unvented HWC solution is fairly simple in that no pumps are required, and you get mains pressure everywhere. However, they need to be serviced annually, and things like the immersion heater(s) are generally specific to each brand and consequently expensive. Any work on them has to be undertaken by a G3 registered technician. In your case it might involve fewer pipework changes, although I would recommend a 22 mm cold feed to the cylinder.

 

[flameport]

- Cold water in attic
- Hot water in a space upstairs
- Both then pump into the upstairs bathrooms

Thats is an option, but really the one of last resort, only to be considered if the mains pressure / flow really is as bad as you suggest and there is no way of improving it.

Find out what the flow is from the outside tap with it fully open and no hose attached.
Fior the pressure, get one of these: https://www.toolstation.com/mains-water-pressure-test-gauge/p75711
and attach it to either a washing machine outlet, or the outside tap if that has a threaded connector.
You want the pressure with all other outlets closed, and then the pressure with one outlet fully open and water flowing from it.

 

[Gasplumber]

Your water supplier would test it at the boundary stopcock for free. Then you know what you have and what you can have in the house if you throw some money at it.

The unvented route would be your best route I feel.

 

[OvertonPlumber]

300 litres at 6 bar!! Cost is normally prohibitive about 3k. The main only does 9ltrs/min on that job.

 

[muggles]

According to the UU website they provide a min pressure of 7m of static head

Not interested in what their minimum supply expectation is. We need to know what you're actually getting. https://www.screwfix.com/p/monument-tools-mains-water-pressure-test-gauge/82412

 

[Josh1987]

Thank you all.

As my local B&Q is one of the ones that is trialing opening this week I will try and pop down and get a proper pressure gauge, as opposed to the DIY option of a bucket and iphone timer and get some proper readings on here.

One of the conversations I have had separately over the weekend with someone was to change, what we think, is the old lead pipe from the mains to the stopcock in the kitchen to 22mm alcathene pipe, this will obviously have a cost implication as I presume a trench will be required through the front driveway - however it if it increases the pressure sufficiently, it would save space and agro thereafter.

However what I can't get my head around is that, increasing to 22mm up to the stopcock is increasing the volume into the house but if the rest of the house remains on 15mm pipework then does the overall flow rate achieved actually change?

I am an overthinker at the best of times, so lockdown isn't helping around this!

 

[oldbuffer]

Don't confuse pressure and flow rate. Pressure is the force behind the water pushing it through the pipes and fittings. Flow is what you get out at a particular point, and is a function of the pressure pushing the water and the forces resisting that pressure. The main forces are gravity, which reduces the pressure by about 0.1 bar for every metre above the incoming water's height, and friction causing "wasted" pressure in overcoming bends, restrictions etc.
With your bucket and timer you have been measuring flow rate. You need a pressure gauge to measure pressure.

 

[Josh1987]

Hi all

Finally got the right bits of kit to test everything at the outdoor tap.

With no other taps on;

Pressure 2.75-3 Bar
Flow Rate 10.07litres per min - which is about 2-2.5 higher than the kitchen

With the tap in the garage fully opened;

Pressure 1Bar - just!
Flow rate down to 5.49litres per min

The flow rate differential is putting into numbers quite clearly what you can see/feel when running the taps.

Are these sorts of ranges normal?

@oldbuffer on to your previous comment re pressure and flow, whilst 10.07l/min isn't the highest rate going, is more of the issue lack of pressure to maintain this as other taps open up

Thank you again

 

[Madrab]

Are these sorts of ranges normal?

There isn't really such a thing.

The suppliers (UU) have a standard min that they have to supply you as per their service agreement which according to you in 0.75bar @ 9L/Min.

Given your readings then you have just over the min flow your supplier should deliver with a higher standing pressure but the fact it drops significantly when you open more than one outlet suggest that your supply pipework may be impacting on what your mains can deliver. What size/type of pipe is connected to your mains stop tap?

The fact you are seeing such a significant drop to the kitchen tap though suggests either the pipework to the tap is restricted (flexi pipes, lots of bends, flow restricter/aerator in the tap etc)

 

[muggles]

So is that 3 bar with everything turned off, or 3 bar with one outlet open? If it's with an outlet open, what's the pressure with nothing turned on?

 

[Josh1987]

@muggles not sure if I have confused matters.

With no taps turned on - and the pressure gauge attached to the outside tap then its 3 bars and with no other taps turned on the flow out of the outside tap is 10.07litres

When a tap in the house is left on and then the pressure gauge is attached to the outside tap its 1bar and 5.49litres

@Madrab do you mean the pipework before - or the pipework after the stoptap?

 

[muggles]

Ah OK, got it. Sounds like a restriction on your incoming main in that case. You should get your network operator to test at the outside stopcock for you, and that will establish whether a new main into the property will help. The alternative is to find space for an accumulator somewhere

 

[hard-work]

1. As others have suggested, it's unlikely you could run two electric showers. Most homes have electricity board fuses of 100 or 80 amps. A 10kW shower uses roughly 40 amps, so two of those and you are very close to the limit. Boil a kettle and you could be over the limit of an incoming 80 amps.

You will find using the diversity factor calcs he will be OK.

 

[hard-work]

Use cold water accumulator - the size of a cylinder - if cold water main flow cannot be improved. Need to test the incoming static pressure. Could be in the loft. Will work well with the combi. Forget gravity tanks, pumps, etc.