He says ... she says ...

[BW2]

the plumber says
no problem mate … it’s all plastic these days … you just push fit them all together … 15mil … interesting job … just choose some fittings & give me a call …

the mixer / tap / shower head saleslady says
… nice choice of fittings, sir … 15mm? no, you’ll need 22mm pipework …

so, I thought I’d try plumber no. 2
plastic plus pressure? … no … could well blow the fittings apart … much better to use copper … 22mm? mmm well yes, if that’s what you want … compression fittings can leak over the years … best soldered & done with it … leaks? No, it won’t.

So – I’m just the chippy for the moment. Maybe it’s time I learnt some plumbing basics.

The plan is …
A shower system – unvented gravity fed hot & cold, but then pumped to up to pressure.
Pump’s got to be close to the tank (I’m told), then runs under the floor 10m through ceiling void (runs between the joists – no cutting or notching) – all accessible now, but later it won’t be as it’s getting a beautiful T&G wooden floor on top. What about pipe support? What about expansion for this distance – noises & sagging on the pipes? (My central heating pipes all expand & click away every morning – I’m sure they’re wearing themselves through).

Last couple of metres to the shower is behind a stud wall – all accessible for now, but later it’ll all be boarded up, tanked, tiled, locked & bolted.

 

[doitall]

First lesson, whats an unvented gravity hot and cold. If you have an unvented cylinder then it will be connected to the mains, unless you are going to use a break tank and pump the water into the cylinder, as you can see it's important to get the facts right ish or ask.

A good plumber will use copper or plastic depends on what he's confident with, I prefer copper, whichever he uses must be well clipped every 1.2-1.5m

 

[BW2]

Ok doitall – point taken – I didn’t explain that very well.

In fact, now I re-read it, I got that bit completely wrong – I do apologise.

Start again - I’ve got an (unpressurised) vented central heating system.

The hot water’s coming from the hot tank (unpressurised) in the loft, and the cold is coming from the cold tank just above it. This new shower is also in the loft – hence the pump to get some pressure.

 

[doitall]

Ok so you are going to install an Negative head pump next to the cylinder and pump the hot and cold supplies to the shower, no problem, provided you keep the cold feed to the cylinder in 28mm copper and use an essex or similar made for purpose connection for the hot to the pump, better still you may have a secondary return tapping on the cylinder.

I would still use copper at least for the exposed pipework, under the floor you can use either or both provided you fix it well.

Reading that again if the shower head is below the pump you could use a positive head pump.

 

[BW2]

Thanks for your thoughts doitall – it’s just the stuff I need to know.

The hot water cylinder is on the floor of the loft, cold water tank is about 2m above, and shower head is going to be about the same – ie level with the bottom of the cold tank. Pump can go anywhere at the moment.

What about the size of the pipe from the pump to the shower – plumber or saleslady? Thinking about it - I suppose that’s a bit of a rude question to ask a group of plumbing professionals – 15mm it is then.

Any problem with the 10m of copper in a straight line heating up & cooling down all the time? How to stop it creaking & clicking ? or is it just one of those things?

 

[doitall]

If the shower head is that high get a negative head pump, it needs to be level or lower than the bottom of the cylinder, I would take the pipe in 22mm at least to where it rises, see what the pump manufacturers say

Try and lag as much as possible under the floor

 

[bengasman]

For future reference:
Sales assistant does not have a clue what he is on about.
If he did, he would not work for 5 quid an hour as a sales assistant.

As a rule of thumb, do not use anything other than soldered joints when they will be hidden by plaster, tiles or anything else that makes them completely inaccessible.

 

[BW2]

Many thanks Doitall & Bengasman

At least I can have some sort of a sensible conversation now with the mysterious forces that move the waters.

A further thought occurs …

My new shower is going to be on the end of about 15m of 22mm pipe – the hot water cylinder’s on the other end. So I’m thinking that when I switch on in the morning, I’m going to get about a minute’s worth of refreshingly icy water before any hint of the warm stuff arrives.

What do they do in hotels & places, when you can scald yourself the second you turn the tap on? How could I do the same - by priming the pipe with hot water somehow just before I turn the main tap on – I imagine?