converting basin to mains supply

[lesshaste]

First off, you will notice immediately I am not a plumber so I apologise for wildly incorrect assumptions/terminology in advance.

We have just noticed, after having drunk from the bathroom basin for months, that it is fed from the header tank in the loft and not the mains supply. Furthermore, if you don't turn it on a for a couple days the water comes out brown for a minute or so. It is also often quite warm, presumably as the tank in the loft heats up.

The question is, what is the best (and not too expensive) way to convert this to fresh water mains supply? I have called a couple of plumbers and, apart from quoting anything from 1 hour to 1 day, mumble something about the system being out of "balance" if you only convert the basin. This seems a little worrying so I need some solid advice.

To fill in the picture, there is a basic and old looking boiler downstairs and a hot water tank about 1 metre from the bathroom. The bathroom has a bath and an electic shower (which is fed from the mains) and there is one toilet in the house. Oh yes, the pipes in the bathroom are lead too :)

Any help much appreciated.

Raphael P.S. If anyone can recommend a half honest/decent plumber that will travel to London E3 that would be even better!

[Ian Stirling]

Bullshit, as they want to do more work - however it may not quite be, as it will cause problems if you want to put a mixer tap there. Also, turning on the cold tap may 'gush', as its pressure may be higher.

The simplest and cheapest way is to turn off the mains supply to the header tank. After this, cut and insert a T junction into the cold water supply pipe. Now, route a pipe, using elbows/... to where the existing cold pipe exits the header tank. Drain the tank, cut the pipe, put a end cap on the end. On the now free end, connect up the pipe you've t'd off the supply pipe. Job done. For best effect, you may want to add a restrictor to the tap, so that it does not gush all over the bathroom, if this is a problem.

If the pipes are lead, this all gets a bit harder, as the fittings are a bit more expensive. I'd get myself up into the attic, and have a look.

[lesshaste]

Thanks very much. Do I have to worry about the toilet and the type of taps in the bath and basin once this conversion has been done to higher pressure mains supply?

Raphael

[Wingedcat]

Am I being completely stupid here or would this method have the effect of pressurising the domestic hot water tank to mains pressure? Seeing as it is usually pressurised by only a meter or so of head between the cylinder and the header tank, surely you could end up bursting the tank? This is why pressurised hot water storage systems are bullet proof and have to be installed by approved contractors no?

Or am I being thick?

Luke

[Christian McArdle]

He only suggested doing it for the cold water outlet from the tank. The hot water cylinder feed should be unaffected and still be fed from the tank. The hot water cylinder outlet is usually separate for two reasons. Firstly, it enables greater flow (particularly when pumped) and secondly, it is a safety measure, as you normally design it so that the hot feed uncovers before the cold, so that the water runs cold before it runs out. Otherwise, it could go hot, causing scalds.

Christian.

[Wingedcat]

Fair play - it was when he was on about "draining the tank", I didn't realise it was a temporary draining and I thought he was suggesting decommisioning it permanently.

There are two types of toilet valve, one for mains pressure and one for low pressure so this will probably have to be changed.

The taps may or may not leak depending on what condition the washers, seats and stems are in. You will find however that the cold water will spurt out like nobody's business and the hot will be as before, so if you have a mixer shower or plan to fit one in the future, it may present problems achieving a comfortable temperature blend. It might also contravene water bye-laws depending on the type bought unless you fit double-check valves. (these ensure water can only flow in the intended direction).

The plumbing itself might not take too kindly to the large increase in pressure and you might find joints bursting apart. To be honest I don't know much about the strength of lead joints.

Luke

[Ian Stirling]

As others have said - possibly. You need to go up into the attic and investigate. Is the piping round the tank copper or lead? What sort of walls - might feeding plastic pipe down behind be a possibility, ...

[Set Square]

If the only reason for making the change is to get clean mains water - rather than dubious stored water - to the basin for drinking, I would convert *just* the basin to mains and leave the bath and toilet colds feeds as they are.

You say that you have a mains-fed electric shower in the bathroom. In that case, blank off the existing feed to the basin's cold tap and plumb in a new feed which is tee'd into the mains feed to the shower.

Does the basin have separate hot and cold taps, or a mixer? If the latter, you are supposed to install a double check valve in the mains cold feed to stop contaminated water from finding its way back into the mains.

[Ian_m]

In my last house whilst re-doing the bathroom, I discovered the cold water feed to the loft tank passed under the floor under the bath. Whilst bath was out, I lifted a board or two and just tee'ed into it and fed a run in plastic to the bathroom sink to get mains water to tap. Remember to include a thumb valve to reduce the pressure and/or match to hot tap pressure.

[Ian Stirling]

But in practice, this is going to be lots more work, as nobody will have run seperate pipes to the bathroom, just hot/cold. If the OP is willing to live with lack of stored cold water when a water failure happens, then this may be simplest.

[Set Square]

I don't think you can have read the rest of what I wrote!

The OP already has a mains cold feed (in addition to the afore-mentioned gravity hot and cold feeds) in the bathroom to run an electric shower. I was simply suggesting tee-ing into that for the basin cold - and blanking off just that bit of the gravity cold feed. The bath cold tap and the toilet can continue to be fed from the tank in the attic - since no-one wants to drink either of these!

If the mains fails, it will only be the basin which doesn't have any cold water (until all the water in the tank is used up).

[lesshaste]

Thanks very much. Seems by the far the simplest solution. One thing that is confusing me is this talk of the cold tap "gushing" once I convert the basin to mains supply. What do they do in countries where everything is on mains supply? Do they have different taps? Do taps have low and high pressure settings in some way? Raphael

[Christian McArdle]

It's just that the mains cold will show up the pathetic hot flow as they will be easily compared side by side.

Christian.