Domestic Plumbing and Shower Feeds

[Big Al]

Hi All

My first post so please be patient! I have just started refurbishing the bathroom in my 15 year old house. Investigation of the plumbing has confused me...

The water system is gravity feed with a cold tank in the loft and hot in the airing cupboard. The hot is heated overnight on Economy 7. There is currently a gravity fed shower in one of the bedrooms. I intend to remove this and ideally just divert the existing plumbing into the bathroom for a new shower.

Now the confusion. The cold supply for the shower has been taken as a

15mm tap from the main 22mm feed from the cold tank in the loft. The hot supply has been taken as a 15mm tap from the 22mm riser from the hot water tank. In addition, this 15mm feed is tapped in turn with a 15mm pipe to feed the bathroom basin below. The first thing to point out is that this all works, but 2 questions arise:

1: I was always under the impression that all hot feeds should be taken from below the T coming out of the hot tank and not above. Am I mistaken?

2: I wish to fit a pump to the new shower. Even having read the numerous threads on how to do this I must ask the question: Can I just hook into these hot and cold feeds and hey presto!?

Many thanks in advance.

Alun

----- | | ---| | | | | ------ | | | | | | | | | | | | | | | | | | | | |------| | | | ---|--- | | | | | | | | | | | | | | | | | HW | | | | | | | | | | -| | | |-----Bath'm Sink(Hot)---->

| --- --- | |

[Fash]

Surely this just means that if we define the shower feed (+ basin) as the top feed this is the T you refer to and all other hot feeds come out below it. Therefore this doesn't seem like a real problem just one of definition.

For this one it depends on the other hot feeds and how big a pump you intend to fit. Theoretically if you are pumping the hot feed it would be advisable to fit a separate hot outlet to the tank to avoid any problems with other hot feeds sucking in air if anyone opens other taps while the shower is running. However you will almost certainly get away with it so I would just try it. It's easy to test if theres a problem: with the (now pumped) shower running try opening other hot outlets, if water comes out of them then you are OK. Worst case for test is basically every hot tap outlet on and if water still comes out of all of them (even if slower than normal) there's no problem. If water doesn't come out then you will need to reconnect the shower to a separate feed from the tank. The same applies to the cold water (i.e. if there's a problem the answer is a separate feed from the cold tank) but you are probably less likely to have a problem with the cold since the kitchen sink and maybe other things like toilets will be connected to the rising main and not the cold water tank. I ran something like this in my old house and never had any problems. Kitchen hot tap was a bit slow when the shower was on but how often are you running the kitchen tap while showering and if it takes a while to fill the kitchen sink who cares!

Sink(Hot)---->

[mungoh]

Hi Alun, Firstly, I'm not a plumber hence these words will be outranked by the more experienced people here in this newsgroup.

The setup you described was similar to the one in my parents home many years ago. The problem was, when anyone downstairs used the hot tap this caused the shower to run cold... eeek!

The solution was to "fatten" the cold supply from cold (loft) tank (Mathew Marks would quickly post that it's a "cistern" in the loft, not a "tank" :-) down to the hot tank so that any draw from the tank didn't reduce the level of water in the hot riser from the hot tank (the expansion pipe). In my parents house the low-level drawoff of hot water caused the water in the expansion pipe to drop below the T-piece tap-off so that the shower wasn't fed with any hot water at all.

Once the old 22mm feed was uprated to 28mm, the freezing shower never reoccured.

By fattening pipes you risk drawing more hot water along the pipe which is unused when you turn off the tap (or shower), which makes it go cold and thus you need to draw more through said pipes when you need hot water an hour or two later. So fattening beyond a limit is counter-productive.

I have no qualms over fattening cold pipes. When I replaced my loft storage cistern a couple of years ago the pipework down to the hot tank was also upgraded from 22mm to 28mm. Tis a b*gger when you don't tighten the compression joints adequately: 28mm pipes can throw a ton of water at a surprised DIYer!

I plan to install an en-suite over the coming winter and feed the new shower via a pump. I also plan to supply the pump with 22mm pipework, reducing it to 15mm if required for the pump (what size inlets are "standard" pumps built with?).

I feel that overdoing the pipework up to a pump must be better than using just adequate sized pipes, but this is just my prejudice and is open to being shot down by others here! :-)

Can others comment whether this presumption is accurate, and also would it be better to continue in (say) 22mm pipework from the pump to the shower as well?

I'll leave others to detail the various "flanges" that might be employed to ensure continuous flow.

So if it were me, I'd beef things up as a contingency for an aggressive pump's demands.

HTH

Mungo

[Big Al]

Fash / Mungo

Many thanks for the feedback. I think I will just `suck it and see`. Or maybe the pump will...

Regards

Alun

[mungoh]

If you are going to do any lengthy pipework you may care to install fatter pipes which won't cost that much more than thinner ones. I'm just considering the worst case that might occur when your "suck it and see" doesn't work out (fingers crossed it does, but I'm a natural born pessimist. :-)

Of course, for heat retention as well as to stop pipework freezing you ought to lag every pipe all the way too.

Mungo

Heard the one about the bloke that was SO narrow-minded he could look through a keyhole with both eyes at once! :-)