plumbing gone wrong

[charlienospam]

Hi,

Apologies that this isn't strictly 'DIY'!!

I'm having a new bathroom fitted and after they left today I noticed that there was water coming out of the cold water tank overflow pipe. Had a look in the loft and the water level in the cold tank was indeed much higher than normal and had risen over the top of the overflow pipe. We actually have 2 cold water tanks in the loft that are connected by a short pipe (no idea why there are 2?) . The water was entering the tank from an inlet pipe low down on the second tank (not from the tank that has the ball valve) When I turn the mains water off the water stops entering. The plumbers had just installed a new bath and had been complaining about the complicated old pipework under that bathroom floor so I'm working on the assumption that they messed up somehow- any idea what they could have done?

thanks Charlie

[A.Lee]

You've got 2 tanks to get a higher pressure for the hot water.

Which tank is overflowing? The one with the ball valve, or the 2nd tank?

Either way, it is likely to be a leaking ball valve washer. Probably 10p for the washer if you can buy them separately. The one with the ball valve should have its overflow a little lower than the 2nd tanks overflow - so if the inlet pipe/ball valve does leak, it will not cause a flood over to the 2nd tank. Alan.

[charlienospam]

The one that's overflowing is the one with the ball valve but as a I said I'm certain that isn't the problem. The water is coming in via a pipe near the bottom of the other tank (the one without the ball valve)Every time I turn the mains water back on it comes in pretty fast. I've checked the ball valve and it seems fine.

If you don't mind me asking, can you explain how having these 2 connected tanks will give me higher pressure for the hot water?

thanks Charlie

[cj]

Hi Just a thought but did you have a Bidet in the bathroom or a non electric shower?

If so your dual tanks may be for the cold feed to the Bidet & or shower . Again,if so the plumber may have connected the mains cold feed to the tank feed under the bathroom floor assuming that the bidet/shower was mains fed before the work was done.

Hope this makes sense.

CJ

[Geoff]

So what is connected to the ball valve? Possibly the ball valve is in the wrong tank and should be connected to the pipe you say is letting the water in as that sounds like your mains supply. But I don't understand what you mean by "the pipe near the bottom of the other tank" Is this under the water?

Alternatively - your plumbers haven't traced the piping properly and have made wrong connections.

[A.Lee]

The tank/s in the loft feeds the hot water cylinder. The bigger the tank, the more pressure is in the hot water outlet, as there is, basically, more weight pushing the water down the pipe. As there is usually limited room getting access to the loft, a work around for this is to fit 2 smaller tanks instead of one big one.

For normal use of water, 1 header tank is enough. If however you'd like a shower, then it certainly helps to have the extra pressure for a faster water flow. Alan.

[Alan]

In message , [e-mail] wrote

Your plumber has connected the rising main to the tank outlet?

[Alan]

Wrong. The heigher the head the more pressure, the quantity of water at the same head height is irrelevant. 2 (or any number of tanks for tha matter) connected with pipes will all level to the same height, and therefore not effect the pressure of water delivered to the taps at all. The reason for multiple tanks is to increase the quantity of water stored where there isn't enough space for one large one, and where one smaller tank cannot store enough to satisfy demand.

Alan.

[crb]

through which the water is entering the tank is a feed pipe to a shower unit or mixer tap that has a defective seal such that cold water from the mains is leaking across the seal into the lower-pressure hot side and backfilling the cold water tank. If you have a stop c*ck fitted to the hot water feed to that shower or mixer tap then closing the stop c*ck will prove the point.

As far as two tanks are concerned, it does not increase the pressure, but it does stop the hot water running out when running a bath, due to lack of capacity in the cold water storage tank - for instance as the result of a restrictor in the ball valve feed to the tank.

CRB

[D Moodie]

normally one tank is a smaller header tank for the central heating

you are confusing flow rate and pressure, they are seperate quantities. Pressure is related to the head of water. i.e the height of the tank to teh shower, say. Flow rate will be dependent upon sizes of pipes and condition of valves.

cheers

David

[Doctor Drivel]

It isn't. It is to give greater storage.

[Doctor Drivel]

You need to understand water systems better.

[robgraham]

I don't think there is any question mark required - if water is flowing from the pipe at the *bottom* of the tank then that actually is the outlet and I would have thought that the only source of the inflow would be the mains.

The question really is which outlet is it, and even more alarmingly could it be the outlet to the HW tank which is now being pressurised to mains pressure.

Personally I would switch off your water at the rising main if you can't isolate it nearer the tanks system and get the plumber - actually any plumber - back in first thing to resolve it as you could have a nasty surprise on your hands. Release all pressure by opening the taps for several minutes.

Rob

[newshound]

You may be able to get two smaller tanks slightly higher though!

[Dave Plowman (News)]

What are the rough dimensions? Usually two because there isn't enough room for one large one - or access via the hatch etc made it the only way to replace the original.

[tinnews]

Rubbish. I was going to say this the first time around but refrained.

The size of the tank makes no difference whatsoever to the pressure, the only thing that affects pressure is the height of the water in the tank.

[Andy Champ]

I've got too s**ing great big ones, apparently because the house was designed with 2 bathrooms (although one has always been a shower) which as far as I can tell is to allow an entire family of 5 to have baths without needing to wait for the mains to refill the tanks.

Except they'd have to be cold baths after the first!

Andy

[John]

Perhaps the original plumber made the same mistake and thought that two tanks made twice the pressure!

Good insurance against water supply failures.

I suspect that it might be a simple case of ball valve fatigue brought about by something being tinkered with.

[John]

Many houses were fitted with large water tanks to compensate for water supply failures or pressure variations. The down side is that this leads to longer storage times. This in turn allows bacteria time to grow and can affect health. The modern move to showers reduces water use further and they create aerosols of contaminated water. This is bad. Many deseases can be caused this way, Legionaires Desease being amonst the best known. We're going through a program of removing our large tanks at work and replacing them with smaller ones. Normally there should only be 24hrs storage.

John

[RobertL]

I've several times come across this mistaken belief and seen people fit huge tanks low down rather than a smaller one as high as they could get it. Another related myth is that it's the height of the bottom of the tank that determins the pressure rather than the height of the water surface.

Robert