Water pressure loss Drainage and wastage systems and plumbing help, advice and answers

[SJLoveday]

Hi There, I thought I'd find this topic in the projects section... anyway, our water suffers a pressure drop when more than one appliance is being used, eg, 2 taps at the same time, or a shower and a toilet, etc. No less than 3 different plumbers have looked at it, and all have declared it impossible. One said we have 4 bar pressure at the mains. Nevertheless, despite the plumbers' opinions, the pressure continues to drop. I don't know about the bars, but a t-joint blew out a while ago and the jet that came roaring out was unbelievable, so I obviously the intrisic pressure is high. So, how can we have such high pressure and yet such drops? Most of the tubing in the house is standard black alky, although some has been replaced with HepO2. Any advice would be very appreciated and I'm happy to supply any more details, thanks.

[plumbbob]

Maybe what is confusing the issue here is how the flow rate affects the pressure.

The house I worked at today had little more than 2 bar pressure so believe me, your 4 bar is pretty much on the above average side so in other words, good.

So if the water pressure is good, how can the flow rate be poor? Well, simple, it is all down to the bore of the main supplying your house. It doesn't matter what pressure you have, if enough water can't get up the pipe to supply both the outlets you mention at once, then the pressure will fall significantly.

How much loss there will be depends on several factors. the diameter of the incoming main, the distance the main travels from the road, and if there are any restrictions in the pipe such as limescale. Even a partially closed stop tap will restrict flow.

Generally, the only answer to increase flow is to replace the incoming main.

[SJLoveday]

Hi, I noted that I had one reply but in fact there isn't one... I don't get it. Meanwhile, if I've had no replies due to me overlooking the answer in some other section could someone point me in the right direction? I'm floundering a bit... Cheers

[plumbbob]

Remember all entries are moderated before being published so will take some time to appear.

[SJLoveday]

Hi Plumbob and thanks for the reply ! The pipe from the main to our external stopcock is 4-cm diameter alky and the distance from the main to there is about 6 feet. From the external stopcock into our house there's more 4-cm diameter alky, about 2 feet's worth, and then it connects to a 3-way distributor (I don't know what this is called but it has 3 independent controllers, having the same function as stopcocks).

Anyway, I would have thought a 4-cm bore would have been enough? It seems pretty big. In fact the local council guy who came to look at the postplumbing work even seemed a bit put out that the plumber had installed such a large pipe. What do you think? Is a 4-cm bore over about 8 feet the prob?

I know you mentioned scale but there isn't any in this area, so at least that's eliminated.

Sorry about being quick off the mark earlier, but I hadn't read about the moderation thing properly! Cheers.

[htg engineer]

Do you have a water softener ? sometimes they're forgotten about and never serviced, it could be blocked.

You seem to be confusing pressure and flow rate, the flow rate is the problem, which could be caused by a restriction in the pipework.

You could tee into the pipe just after the mains stop tap, and see what the flow rate is like (connect a washing machine valve and hose), if it's also low, it's either a faulty stop tap or the mains. If the flow rate there is good then there could be a problem with the internal pipework (kinked or damaged) or your taps.


htg

[SJLoveday]

Thanks HTG, in order, no there's no softener. On the other hand, I'll definitely follow up on finding out the flow rate. Here's hoping ! cheers.