power shower problems

[mp]

Hi all

I'm about to install a power shower (I can imagine it's been covered umpteen times) but despite doing a previous search about my problem I've seen no answers/solutions.

The problem is that the cold water feed to the shower mixer comes direct from the loft water tank (normal) DOWN through to the mixer, whereas the hot water comes from the airing cupboard through the floorboards and UP to the mixer.

So my problem is getting the pipes close enough for the pump to connect to. I can't use a post-mixer pump due to wall cavity being so thin (barrats house!).

Solution - I was thinking of feeding the cold water DOWN to the airing cupboard and then feed it UP back in the loft to rejoin where cut into it. The problem I see with this is extra work for the pump, ineffective pressure (15mm pipes not 22mm) or the need for a negative feed switch (which then raises the question about the hot water feed being positive).

In an ideal world I'd feed the cold water down to the airing cupboard and then relay through the floorboards (same as the hot water feed), but the floorboards are larges T&G and very tough to get access to.

Thanks for any thoughts.

MRJP

[BigWallop]

You already have a cold water supply to your hot water tank, so why not tap in to that?

[John Stumbles]

The problem will be that you have a high point in the pipework in which air will accumulate. You'll need to fit an air vent at this point. You may be OK with an automatic air vent. The 15mm pipework shouldn't be a problem and you won't need a negative head kit or switch.

Can you really not run plastic pipe from the airing cupboard up to the mixer?

[Doctor Evil]

You really haven't a clue. Please do not give advise on fields you know nothing about. The cold for the shower comes from the cold tank.

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[MP]

Hi Bigwallop

Is the cold water feed into the hot water tank a dedicated feed? (so I won't get scolded if someone turns on a cold water tap elsewhere in the house).

[MP]

Hi John

Bigwallop suggested using the cold water feed for the hot water tank, which seems like cracking idea.

I'm getting used to the idea that I'll have to access the floorboards and use pipe (plastic i presume is okay for the pressure passing through it) work to join up at the mixer.

PS - Is it possible to get longer attachments to the pump to replace tha come with the pump, they seem rather short.

Thanx

[Set Square]

Whereas the cold feed to the hot tank comes from . . .yes, you've guessed it . . .the cold tank!

Having said that, the shower really does need a dedicated feed from the cold tank - and not one shared with the feed to the hot tank. It also needs to be taken from a *lower* point than the cold take-off to the hot tank so that, in the event of the cold tank emptying, the hot stops running first.

[BigWallop]

So a new and dedicated pipe from the cold tank would continue to supply cold water, even with the cold tank empty? Oh right. Both hot water cylinder and cold water tap supplies are from the same cold water storage tank. The pressures to all the taps and appliances will all be equal, barring stupid forms of pipework of course. So I don't see any need to complicate the supply to one single new appliance that is being added to an already stable system.

Where do you people live? :-)

[BigWallop]

The hot water tank is being fed from one single line of pipework. This single line of pipework is cold. It's only when the water sits in the hot water tank that you begin to heat it. Does you cold water storage tank get hot? I should hope not.

The supply pipe to the hot water cylinder is large enough, if made 22 mm dia' pipe, to supply both the cold feed to the pump and still have plenty water left over to keep the hot water tank replenished and supply a hot feed to the pump as well.

Two things. Is the cold supply to the hot water cylinder quite a straight run down? And does the hot water run out of the bath taps at a much lower rate than cold? I'm not talking pressure wise here, I mean at a very much slower rate (quantity per) than the cold.

These can be checked by timing the filling of a large pot or bucket. From empty, turn on the cold tap and fill it up. From empty again, turn on the hot tap and fill it up. Deduct the times from each. If there is a huge difference, and I can't there being, then you'll need to supply a pump from two totally separate hot and cold supplies. If there is only a couple of seconds difference, then you're OK to tap in to the cold and hot pipework right beside the hot tank.

I was going to go all technical, but this explanation should be OK to understand.

Don't over engineer it, you'll only f*ck it up. :-)

[Set Square]

You're not listening!

With a power shower going full tilt, you will potentially be removing water from the cold tank faster than the mains supply can replenish it. So the level will drop. When the level drops below a take-off point, that take-off point obviously won't supply any more water.

The take-off point for the cold feed to the hot cylinder - which in turn pushes hot water out of the cylinder to the shower pump - needs to be

*higher* up the cold tank than the take-off point for the cold feed to the shower pump. Then, when the level drops, it will cause the hot feed to the shower to stop first, with the cold feed still running. If it were the other way round, you could have scaldingly hot water coming out of the shower.

I hope that makes it clear!

[Doctor Evil]

This is a stupid idea. The cold "must" have an independent cold supply from the cold water storage tank.

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[Doctor Evil]

You really have not got a clue. Please shut up. people are requesting advice. You have none to give.

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[BigWallop]

So you're saying it would be better if the cold supply was direct from the mains? Or is your own contradiction a part of not understanding the workings of creating a head of water to a shower head?

You say that the cold water storage tank may empty if the shower used:

"> With a power shower going full tilt, you will potentially be removing water

Then you say to take yet another cold water supply from the cold water storage tank:

"The take-off point for the cold feed to the hot cylinder - which in turn

Or am I missing your point here?

There are already two outlets taken from the cold water storage tank. One supplies the hot water, and the other supplies the cold. Both outlets will be near the bottom, if not actually through the bottom, of the cold water storage tank. Therefore both outlets will be supplying their respective appliances with an equal amount of head (pressure).

A pump for a system that is going to be sited slightly higher than a normal appliance, in this case the shower, only needs to supply a slight increase in the pressure of the supplied water to create the correct head (pressure) to make the whole thing work properly.

A shower pump isn't a massive taker of water, that's why they are only supplied with narrow bore pipes. In fact, the shower will be using only around a quarter the amount of water flow rate that running both huge 3/4'' taps on the bath will. Even if the pump were to be supplied with 28 mm bore pipework on both the inlet and outlet sides, the pump would still only be able to draw about a quarter the amount of water that the pipes can supply to it.

I advise using the cold supply in and the hot supply out of the hot water storage cylinder because, when the shower is in use the cold supply feeding the rest of the house will be able to supply the taps without creating any pressure difference to the shower supply. It also creates the situation of having both cold and hot supplies at an equal pressure to both sides of the pump, and so make things easier to balance at the mixer valve.

[Set Square]

I said no such thing! The shower pump must have equal pressure on its hot and cold feeds - so they must both be gravity feeds from the cold tank

I understand the Physics of it all perfectly - but I'm not convinced that you do.

I'm saying that *all* of the water going to the shower is coming from the cold tank - the cold going directly, and the hot going via the hot cylinder

YES!!

A decent power shower will deliver 15 litres or more per minute. Many domestic cold supplies can deliver little more than 10 litres per minute - so with the shower going full tilt, the level in the tank will go *down* even if no-one else in the house is using any water.

It's important that the shower doesn't run out of cold water before it runs out of hot - hence the need to have to cold feed for the shower at a lower level in the tank than the hot feed.

I cannot explain it any more clearly!

If you *still* can't understand go and ask all the Little Wallops and Middle Wallops in your family - maybe they can explain it better!

[BillP]

HI There,

The simplest method for your existing installation would be to do as you suggest. Put the pump in the airing cupboard. Route the existing shower cold feed from the tank down to the airing cupboard in 22m. Take the pumped hot outlet to the existing shower hot feed, and take the pumped cold up into the loft to the original cold feed.

Although the up and over run on the cold feed is not ideal, I woulnd't expect this to cause problems with air locks as it's on the pumped output side of the run.

You could do as Big Wallop suggests and take the cold feed from the input feed to the hot water tank. Some manufacturers give this method as an option. Yes the ideal method is a dedicated feed from the cold water tank and Surrey/Essex flanges from the hot water cylinder but you won't get shot if you don't do it that way.

I have scanned a section of a manual for a power shower showing three options for connection www.geocities/wjp_gof/shower.doc

Method 2 shows a cold feed taken from the supply to the hot water tank. You may experience variations in shower temp when other outlets are being used.

The reality of this depends on your cold water installation. If all the other cold water appliances in the house are on high pressure mains, then you won't have a problem. I ran a power shower for years plumbed in this way and it worked fine.

Regards Bill

ps Method 3 illustrates the dialogue between Big Wallop and Set Square.

[BillP]

sorry should be this