Another shower pump question...

[Daryll]

In the next month I've having my boiler, HW cylinder and CW tank replaced.

As we're also thinking about revamping the bathroom in the near future, I'm trying to plan ahead and get the plumbing ready for the posibility of a power shower.

I'll have an extra outlet on the CW tank for the cold feed to the pump, but I'm struggling to figure out how to get the hot feed from the HW cylinder to the pump, which will be in the bathroom...(no room in the airing cupboard)

I'm having a dedicated flange fitted to the HW cylinder, (I can't remember which county it comes from!!), ready to feed a pump, but once the cylinder is installed there will be no way to feed pipework from there to the bathroom.

After this long explanation, comes my question..... can I feed the hot feed back up into the loft, across, then down into the bathroom, and if so, will that need a "negative head" pump or a normal "positive head" pump?

(CW tank is in the loft, HWC is in the airing cupboard, 22mm pipe used for everything.)

Thanks in advance,

Daryll.

 

[Richard C]

..... can I feed the hot feed back up into the loft, across, then down into the bathroom, and if so, will that need a "negative head" pump or a normal "positive head" pump?[/b]

Yes you can feed up & over but weather or not you need a negative head pump depends on how close (vertically) you run the pipes to the bottom of the tank as this is what determines negative head, not the position of the shower head (try not to go below 600mm for positive head), which pump you use, the length of horizontal pipe runs in the loft & if you can achieve a minimum 1 litre/min flow at the shower head under gravity condition (no pump). Up & over loops must also be vented or you will air lock the system in a very short time.

Essex (into the side at the top) is best.

 

[Daryll]

Thanks Richard...

The CW tank will be on 4x2's resting on the rafters, so if I run the pipe down between the rafters the best I can hope for is 8''... 200mm... of head.

So I'll need a negative head pump. even though it will be sitting on the bathroom floor 8 feet below??

My only other option is to try and slide some pipe under the floorboards from the airing cupboard to the bathroom before they fit the new HWC, so its there and ready should we need it...

Daryll

 

[Richard C]

the best I can hope for is 8''... 200mm... of head.
So I'll need a negative head pump. even though it will be sitting on the bathroom floor 8 feet below??

The location of the pump, the bathroom, shower head etc. is not necessarily what dictates a potentially negative head situation, its the distance between the highest point in the pumped system (in this case the up & over pipes) & the underside of the CWS tank. It’s still a positive head relative to the surface of the water in the tank but the flow rate through all the pipe work may not be enough to trigger the flow switches in the pump. Some pumps are better than others (presumably due to the design of the flow switches); Salamander say 600mm min. Stuart Turner 200mm min so your already on the minimum margins for ST. Even if you meet those dimensions, you can still get caught out by the length of horizontal runs at any level & unsuitable isolation valves (not full bore) which will further restrict flow. If flow is not enough to trigger the pump flow switches, it won’t work & that’s why you ideally need that 1 litre/min minimum under gravity at the shower head to be safe.

My only other option is to try and slide some pipe under the floorboards from the airing cupboard to the bathroom before they fit the new HWC, so its there and ready should we need it...

If your going to do it & don’t want the possible expense of a negative head pump, run the pipes under the f/boards now if you have the opportunity but use 22mm not 15mm, as few bends (not elbows) as possible & as few joints under the floor as possible (especially if tiling). I only use soldered copper, not push fit or even compression & I will never use plastic.

 

[Daryll]

Thanks again Richard... I've just been up and had a look under the bath... and the joists run the wrong way...

.....So I'm pretty bu*gered with my Plan A... (under the floor was my initial plan, the "up and over " was someone elses suggestion), unless I decide to lift more floorboards that I really want to..

Down and under will be very tricky to lay the pipes, but a 2.5 m pipe run from HWC to pump, and a definate positive head pump.

Up and over will be easier to lay the pipework, but a 4 - 5 m pipe run and a negative head pump...

... between a rock and a hard place.....


Is there a way of checking this 1Ltr/min rate before I start laying pipes??

 

[Richard C]

Is there a way of checking this 1Ltr/min rate before I start laying pipes??

Think about it ------



No, every situation will be different; your on the margin but it may be OK with an ST; but then again, maybe not.

You will also need vents at the highest point in the loops or the pump will air lock after a while.

 

[Daryll]

Ok, I'll bite the bullet and go the "down and under" route.

One other, possibly dumb, question I have is about the pressure from the shower.

With our current mains pressure electric shower I like to have a high pressure shower, but the Missus prefers a gentler shower... something to do with her not liking the high pressure on her tender bits...

So when we have a pumped shower, can we turn the flow rate / pressure down, or will this damage the pump as the outlet will be restricted??

... or is a pumped shower just "on" or "off"...

Daryll.

 

[Richard C]

You won’t be varying the pump pressure/flow. High volume rain drencher heads tend to be the most fashionable these days & its quiet easy to vary the pressure by turning it down slightly without significantly affecting the water volume; if this doesn’t suit you preference for drilling holes in your head , you need to research what’s available as there are many options.