Water pressure from tank - is there a minimum requirement?

Yorky

I live in new house and have poor pressure form all of the loft cistern-fed taps (hot and cold) in the house. In one of the bathrooms the toilet cistern will not even refill when the sink tap is turned on! This contrasts with the mains pressure which is more than adequate.

Is there a building reg. minimum water pressure requirement for taps coming from the tank? If not, is there a straightforward way of increasing it without too much expense?

Corkey123

if you have the room in the attic you could raise the tank on a platform thereby increasing the pressure. Maybe a change of storage tank might also increase the pressure. I'm sure there are storage tanks suitable for such systems. Giev Heat Merchants a ring and they'll let you know

Yorky

The tank is actually in the loft and all of the rooms it serves are either one or two floors below it.

DublinWriter

Been through a very similar thing myself just recently.

Basically, builder skimped on the plumbing and installed 1/2 inch thick piping from the attic tank to the gas boiler in the utility room off the kitchen.

This meant that the low mass of water in the pipe wasn't enough to even get 1 bar of pressure to the boiler. The boiler won't fire if the pressure is below 1 bar.

The mains pressure was fine, so the plumber I got recently but a feed in from the cold water at ground level to the boiler and all is ok.

The plumber also mentioned that I could can get a pump in the attic to increase pressure.

As you mentioned you live in a new house, then check the width of pipe coming from the attic tank - I've been told that it should be at least 1 inch in diametre.

It could be that your builder skimped on this part of the piping too.

ircoha

DublinWriter wrote:

Been through a very similar thing myself just recently.

Basically, builder skimped on the plumbing and installed 1/2 inch thick piping from the attic tank to the gas boiler in the utility room off the kitchen.

This meant that the low mass of water in the pipe wasn't enough to even get 1 bar of pressure to the boiler. The boiler won't fire if the pressure is below 1 bar.

The mains pressure was fine, so the plumber I got recently but a feed in from the cold water at ground level to the boiler and all is ok.

The plumber also mentioned that I could can get a pump in the attic to increase pressure.

As you mentioned you live in a new house, then check the width of pipe coming from the attic tank - I've been told that it should be at least 1 inch in diametre.

It could be that your builder skimped on this part of the piping too.

Interesting: Static pressure is a function of height and density of liquid only.

Pressure is measured as force over area or say weight over area, eg pound per sqaure inch or psi.

A column of water x feet high will have the same psi, regardless of pipe size.

There must be some other problem.

My recollection of this from science class is as follows:

I bar or 1 atmoshere is = to 760 mm of mercury

Mercury has a density of 13.6 gms/cc

water has a density of 1gm/cc

which means that 760*13.6 = 10.336 metres or c 33 feet of water is required to create a pressure of 1 bar.

Am open to correction here:)

DublinWriter

ircoha wrote:

Pressure is measured as force over area or say weight over area, eg pound per sqaure inch or psi.

Exactly, the pressure will be greater proportional to the size of the area.

Skinny pipes = low pressure.

Yorky

The heating system seem to be in working order, it is just the tap pressure. The plumber actually admitted that the feed to the bathroom in question is half-inch and claims that is standard!

ircoha

Yorky wrote:

I live in new house and have poor pressure form all of the loft cistern-fed taps (hot and cold) in the house. In one of the bathrooms the toilet cistern will not even refill when the sink tap is turned on! Tom JonesThis contrasts with the mains pressure which is more than adequate.Not Tom Jones

Is there a building reg. minimum water pressure requirement for taps coming from the tank? If not, is there a straightforward way of increasing it without too much expense?

Sorry yorkie, went off topic with the bit of science!!

No there is no minimum requirement

Tom Jones= Not unusual, because tap outlet is larger than the outlet in the cistern.

Not Tom Jones = this is usual.

It the pressure at ground level better than upstairs?

Yorky

It the pressure at ground level better than upstairs?

A bit but not much better.

In one of the bathrooms the toilet cistern will not even refill when the sink tap is turned on! Tom JonesThis contrasts with the mains pressure which is more than adequate.Not Tom Jones

Surely not in a modern house?


How much would it cost to fit a pump in the loft for the hot/cold stored water?

DublinWriter

Yorky wrote:

The heating system seem to be in working order, it is just the tap pressure. The plumber actually admitted that the feed to the bathroom in question is half-inch and claims that is standard!

Sounds dodge to me. A half-inch is basically the diametre of your middle-finger, which I think you should have demonstrated to the original plumber!

As I originally mentioned, you can install a pump in your attic, not cheap (around €500 was the price I was quoted) plus it's another bundle of moving parts that will eventually break down at some point.

The other alternative is re-plumbing your attic pipes to 1 inch in diametre, which I would imagine would be even more expensive.

ircoha

In one of the bathrooms the toilet cistern will not even refill when the sink tap is turned on!

Not defending the plumber but the normal way in a b/room is 3/4 to the bath and then 1/2 to whb and head.

the modern cisterns have a v small opening in the filling mechanisn so when the whb tap is opened it is the line of least resistance.

re a pump in attic, not a good idea as u dont need to hear it when u use the head at night, in the attic space it will be V hard to kill the sound.


There are pro plumbers on thsi forum so what follows may be bs

in terms of feeds from the tank it should be 3/4 to base of HWC and 3/4 to bath, I dont believ it needs to be 1"

Reyman

DublinWriter wrote:

Exactly, the pressure will be greater proportional to the size of the area.

Skinny pipes = low pressure.

Spare us please DW we've been over this ground before.

The pressure at the end of a pipe is nothing to do with the diameter of the pipe.

Only the flow rate is dependent on the diameter of the pipe.

Science - physics - fluid mechanics, man! Read Ircoha's post

DublinWriter

Reyman wrote:

Science - physics - fluid mechanics, man! Read Ircoha's post

Pah! A pox on the witchery you call 'science'!

Seriously, as the pressure gradually dropped in my own system I'm starting to think it's down to the pipes furring.

I live in a very very hard water area. For example, I hadn't used the ensuite shower for about 4 months, and the holes in the shower nozzle got all blocked up with calcium deposits.

I wonder if there's anything I can drop in the attic tank like Calgon to help matters?

Now, the only plumbing job that remains in chez DublinWriter is to re-plumb the arse of a job done originally - the rads and hot water tank share a single return so switching the A/B switch does nothing - both get be heated.

iplogger1

I mentioned this in a different thread but no replies yet.
Our plumber who originally was suggesting providing us with
a Grunfos MQS-35 or MQS-45 (peak 3.5 or 4.5 bar respectively)
is now suggesting that he'd install some kind of attic tank
which provides the boost for pressure for showers etc and
which will have pressure reducing valves to allow regulation
of pressure. What exactly are these attic tanks which have
a pressure boosting pump built in ?

forgive my ignorance -- I'm not too savvy with domestic plumbing
despite a degree in Physics

DublinWriter

iplogger1 wrote:

is now suggesting that he'd install some kind of attic tank
which provides the boost for pressure for showers etc

If it's just a problem with a shower, why not install a power shower?

It would be more economical as it has it's own pump and heater which only come on when used, so you wouldn't need to heat an entire tank of water just for a shower.

Plus, as the previous poster said, an attic pump can be quite noisy.

Endymion

ircoha wrote:

Interesting: Static pressure is a function of height and density of liquid only.

Surely you mean Volume, not density. You converted to volume in the end, so there nothing wrong with what you're saying, it's just standard to talk about pressure in terms of height and volume, since these are the variables.

DW, stop talking ****e.

DublinWriter

Carnivore wrote:

DW, stop talking ****e.

Carnivore, stop stalking me! Since when did you have a plumbing system that you had to maintain personally?