low pressure in unvented system

[mcerbm]

Bit of a long story, bare with me please!

I originally had a vented hot water system, I had the bathroom of my 4th floor flat upgraded and part of this was adding a 2 bar pump for the shower. Once it was all finished I noticed two problems:

1) The 100 litre hot water tank, fed by the cold water header tank was emptied within 20 mins of having a shower.
2) The new sink(basin sits on worktop) with elevated tap (including filter) now had unacceptably low water pressure. The water cylinder is raised in a cupboard on the same floor as the batthroom so not much head.

I decided to solve both problems that the vented system had to go. I had two unvented cylinders placed in the loft (small space so hadd to have two to get 200litres hot water) and teed together. The hot and cold pressure from the taps is good, and i have plenty of hot water but the pressure out of the showers has reduced.

I got the plumber to install a pressure guage on the cold water pipe coming into the flat and it shows 1.6bar. I phoned scottishwater hoping to get the mains water pressure tweaked up. The operator I spoke to said they were only obliged to provide 1bar. I got a scottishwater tech to confirm the input pressure to the building was 2.7bar he wasnt sure if it could be increased (I think he was a trainee).

My questions are:

1) I know in a vented system that is open to atmosphere you lose water pressure with height, but is the same true with an unvented sealed system (the 1.6bar was with all taps etc closed and no flow)?
2) Is it possible for the waterboard to increase the pressure to the street?
3) Is it possible to put the 2 bar pump back in for the shower (22mm pipes from the cylinder to the pump, 15mm pipe to the shower valve from the pump)?

Thanks in advance

Blair

 

[SimonJohns]

What is the pressure when you run the taps. Static is not really going to help you when You want a shower

Also where is the gauge located. You will lose 0.1bar for every meter you go up

 

[SafeGasInstall]

Hi Mr Blair, and welcome to the forum
Q1;yes (its call gravity)
Q2;no
Q3: NO as you need a breaker tank UHWC are of the main

 

[mcerbm]

I will check the pressure on the cold mains input into the flat when I get home tonight and repost.

Would it be possible in theory to put a pump in an unvented system downstream from the cylinder if the pipes supplying the pump were larger (22mm) than the output of the pump (15mm) i.e. you are supplying a the pump with a suitable flow so it wont cavitate?

 

[mikegas]

No you can't pump the Mains which is what your unvented cylinder is

 

[SafeGasInstall]

U need your old conventional system re fitted and thef you can bustt it , unfortunately research should have been done before UHWC was fitted !

 

[SafeGasInstall]

U need your old conventional system re fitted and thef you can bustt it , unfortunately research should have been done before UHWC was fitted !

U need your old conventional system refitted and then you CAN boost it ,


Spell mistakes as usual 🙂

 

[dancinplumba]

am of the understanding that you can pump the mains, but you need permission of water supply company to do so, they will usually say no 🙂

 

[PlumbBobBob]

so no point in asking really. it's not allowed and not a good idea.

 

[mcerbm]

Thanks everyone for responses so far. The water pressure on the cold mains into the (4th floor) flat static is 1.6bar. If i run the taps the mains input pressure is showing 1bar as its is flowing. When i shut the taps it goes back up to 1.6bar.

I am hearing from a few of you here that it is a bad idea to feed a pump from the UHWC, could somebody explain why this is? There is a pressure relief valve on the UHWC so momentary high pressure from the mains wouldn't be a problem, if there is low pressure the pump may cavitate i suppose when it doesn't get a great enough flow of water to supply it (equipment damage). Is there a fundamental reason why its unsafe or not a good idea?

 

[SafeGasInstall]

IT IS ILLEGAL , WATER regulation I do knot how much is the fine if you do but wont be below 5k

 

[dancinplumba]

you are sucking water direct from mains, if next door turns tap nowt will come out cos you have sucked it all away by your pump and you could cause cross contamination to mains supply !!!please
🙂

 

[mcerbm]

OK thats sounds convincing enough to me. So is there a solution out there to get a decent pressure shower? I have heard of people using an accumulator to provide the required flow, is this prohibitively expensive, is it the only option I have??

 

[dancinplumba]

no offence but you have to give notice if a pump or booster drawing more than 12 litres per minute is connected directly or indirectly to a supply pipe.
what happens if its less than 12lts ???
regards steve

 

[sheff paul]

Bit of a long story, bare with me please!

I originally had a vented hot water system, I had the bathroom of my 4th floor flat upgraded and part of this was adding a 2 bar pump for the shower. Once it was all finished I noticed two problems:

1) The 100 litre hot water tank, fed by the cold water header tank was emptied within 20 mins of having a shower.
2) The new sink(basin sits on worktop) with elevated tap (including filter) now had unacceptably low water pressure. The water cylinder is raised in a cupboard on the same floor as the batthroom so not much head.

I decided to solve both problems that the vented system had to go. I had two unvented cylinders placed in the loft (small space so hadd to have two to get 200litres hot water) and teed together. The hot and cold pressure from the taps is good, and i have plenty of hot water but the pressure out of the showers has reduced.

I got the plumber to install a pressure guage on the cold water pipe coming into the flat and it shows 1.6bar. I phoned scottishwater hoping to get the mains water pressure tweaked up. The operator I spoke to said they were only obliged to provide 1bar. I got a scottishwater tech to confirm the input pressure to the building was 2.7bar he wasnt sure if it could be increased (I think he was a trainee).

My questions are:

1) I know in a vented system that is open to atmosphere you lose water pressure with height, but is the same true with an unvented sealed system (the 1.6bar was with all taps etc closed and no flow)?
2) Is it possible for the waterboard to increase the pressure to the street?
3) Is it possible to put the 2 bar pump back in for the shower (22mm pipes from the cylinder to the pump, 15mm pipe to the shower valve from the pump)?

Thanks in advance

Blair

i am probably stating the obvious but have you got at least 22mm incoming supply,and the ground floor has 28 mm supply

 

[tipintim]

1.On a vented system to atmoshere you do not to my knowledge loose water preasure at height. If you have a meter square cws, that is a thousand ltre, and a thousand litre is a tone, and 0.5 of a meter is 0.5 of a bar of presure.
2. no
3. no

 

[PlumbBobBob]

no 0.5 meter head isn't 0.5 bar it is 0.05 bar 5 meters head is 0.5 bar.

 

[tipintim]

Steveb, I knew someone would pull me on that one if I was incorrect. Thanks bud,. Its been a while since college, but credit were its due. x

 

[PlumbBobBob]

just remember 10m=1bar

 

[stokecity]

someone has already said that the only way you will get the shower you desire is by installing a break tank, this is your only option to install a pump without breaking regs, unless you want to go back to gravity, the break tank wont cost you much

 

[mcerbm]

Sheff Paul, It is 22mm into the flat, couldn't comment on what size is being supplied at the ground floor.

 

[PlumbBobBob]

you are always going to get lower pressure on the fourth floor than at ground level because for each meter in height the pressure will fall by 0.1bar. there is probably about 3-4 meters for every floor so would be 12-16 meters to the fourth floor which would be a drop of 1.2-1.6bar over the pressure at ground level.