Rising main...or not?

[Ben]

Hi - I have a 15mm pipe in my flat that I initially thought was the rising main for the block. This was based on the following observations:

1)My kitchen cold tap and washing machine are fed from it directly 2)It makes noises that sound like rushing water when people other than me are using water 3)There is a much larger pipe which fills my hot water header tank and then goes to the rest of the building which would appear to be a low pressure cold water pipe

However, as far as I can tell my "riser" comes down from the loft and then into my kitchen, but no further. So it would seem it can't be the rising main because it doesn't go anywhere other than my flat.

But in this is the case then why can I still hear all sorts of horrid noises (and feel the pipe vibrate) whenever cold water is used by me or someone else in the block. It must in some way be mains as my cold tap is run from it...

Cheers,

Ben

[calums]

Ben

It is quite common in many parts of the country to have a rising main going into the loft space of a block of flats. From there it will go into a cold water storage tank which will then feed all the units within the building. Some have separate cold water storage tanks for each apartment, others will share the tank.

My guess on the information that you have supplied is that this is the case and that you are on a shared tank, hence the vibration when someone else draws off water. The only alternative is that there is a rising mains which then branches off into each flat, since its on the same pipe you will get some vibration when someone else draws off water.

The only way to ascertain which it is would be to go into the loft space and see if there is a cold water storage tank (not a header tanks for HW). Depending on the outcome you will either be getting mains pressure water, or else gravity fed.

By the way, one of the reasons for using a cold water storage tank, in addition to meeting old regulations, was if the mains pressure isn't great enough then the flow rate is actually better with a cold water storage tank. It then refills at its leisure between run offs.

Hoping this helps Calum Sabey NewArk Traditional Kitchens 01556 690544

[Ben]

Thanks - and at 0042 as well! The strange thing is I have a pipe which is much wider (maybe 2") and is certainly low pressure cold water.It comes from the loft and feeds all the taps/loo etc except for the kitchen cold. It also disappears into the flat below.

The thin 15mm pipe that makes all the noise feeds only my cold tap and the washing machine. I originally though it was the rising main, except it doesn't go beyond my flat. Might the main rise to the loft and the branch off to the individual flats?

As a test I flushed the loo in my flat. The low pressure wide pipe got very cold, indicating water was flowing into my cistern from it. Then the 15mm pipe started making a racket. This quickly dies away to be replaced with a quiet rushing, then followed by a much longer period of grating and whistling before silence.

This would seem to be in response to the level dropping in the main loft tank (guess??).If it is a branch off the rising main and the tank valve is dodgy it could be transmitting this noise into my flat...? As the valve opens or closes it makes awful noises, and because the tank fills slower as te level rises the second noise lasts longer.

Does this sound reasonable?

Cheers, Ben (who realises it is far too late and is going to bed :-))

[TheScullster]

"Ben" wrote

Ben

Sounds like you are correct to me! Cold water to kitchen taps comes from incoming main so it cannot get contaminated by going via a (possibly open to nasties) storage tank. But storage tank feeds all non-hygienic users (toilets, baths etc which water people should not be drinking). As has been suggested, this storage tank arrangement was accepted practice particularly in areas of low/fluctuating water pressure as it insulates the user from loss or low flow.

Phil

[Ben]

The strange thing is that the rising main seems to rise top the roof... and then fall to the flats, rather than going through each on its way up. If the water isn't actually flowing through my bit of main, but it sounds like it is, is there anything I can do? Perhaps a ruberlinkage somewhere along the pipe...?

Cheers,

Ben

[David Hansen]

On 28 Feb 2007 00:39:59 -0800 someone who may be "Ben" wrote this:-

Perhaps a way of ensuring that there is some water flowing into storage, even if every kitchen tap is open. Without this air might be drawn into the mains more easily.

[Ben]

vibrations along the pipe? It feels like there is water rushing through my "branch", and often it makes all sorts of vibrating noises into the bargain, even though I'm not using water from my branch...

[TheScullster]

"Ben" wrote

Are you responsible for the maintenance of the ball float valve in the storage tank supplying your flat? If so, try replacing it. For some reason float valves tend to become noisy, particularly towards the end of their service life. Usually this is due to a hardening of the sealing washer (in the case of the traditional float valve that is). When I swapped mine out, I found that the washer had "blown" and looked like a sponge but was rock hard. I changed mine to reduce noise!

Also trace the pipe run and look at packing the pipe with flexible pads (pipe insulation is ideal). If any noise is due to physical pipe movement this may help. Finally, if you have a stop c*ck controlling your flat supply only, consider turning this down to a minimum you find acceptable. This should help reduce "in-pipe" noise, but beware if you have a combi boiler, this will affect flow rates for hot as well as cold water.

Phil

[Ben]

Hi - I don't control the loft space, but there is a council plumber coming this afternoon, so I'm just trying to work out what to tell him. It seems that most of the noise is due to transmission alkong the pipe rather than the movement of the pipe itself banging on other things etc. Unfortunately I don't have my own stopcock, but I will ask the plumber when I see him.

Cheers,

Ben

[Ben]

Well, I've certainly worked the system out now. Still trying to get the council to address it, or even just let me hire a plumber - I am aware that councils have better things to spend money on, if it would solve the problem I'd gladly pay him myself. Its just a question of whether the council will let me...

The rising main goes up into the roof space. Before it reaches the storage tank it branches off a series of spurs providing mains water to flats below

The two problems I've been having are water hammer and continuous dripping

So I have suggested fitting a Torbeck side entry valve to quieten filling and reduce hammer. I also assume that each spur must have its own stopcock for ease of maintenance, so I presume I could reduce the pressure to the flat.

Finally the current spur has 7 bends in it as it snakes through almost every room in the two story flat. I have suggested running it straight up existing ductwork from the kitchen, were it is needed, to the roof. This should not, I would have thought, be a particularly large job. It eliminates pipe bends and keeps the pipe itself a long way from the bedroom!

The strange thing is the spur sounds and feels exactly as if it has water flowing through it much of the time, and yet it can't...it must just be vibrations...

Does the above sound reasonable? Cheers,

Ben