Shower pump - reuse existing 22m bath feeds...?

[TimS]

Hi,
We're in the process of converting a bathroom into a shower room, and want to replace the existing bath with a walk-in shower. Along with this, we ideally want to install a "proper" thermostatic shower (probably with a pump) rather than an electric shower.

Having spent some time scouring the forum for information it seems that to get a decent flow rate to the shower all pipework feeding the pump must be 22mm... hence this question:

Now that we've removed the bath I've been able to determine that the feeds to the taps are both 22mm runs - one from the cwt in the loft and the other from the hot cylinder. The basin & WC supplies were then teed off these feeds via 22m to 15m conversion fittings and 15mm pipe.

Rather than installing new dedicated feeds & another take-off from the cylinder, can anyone see a problem with using the original feeds to feed a shower? The shower room would effectively be single use so the feeds would to all intents & purposes be dedicated to the shower while it was being used... the WC won't be used at the same time as the shower for example!

We've got good cold pressure thanks to the loft cwt but the hot's not as good - hence expecting to need a twin-end pump. Assuming this is the case, there's nowhere in the bathroom to fit the pump (and if using the existing feeds don't really want to fit it in the airing cupboard) so we're considering installing it in the loft.

If we fit a negative-head pump (on the basis that it will be located above the hot water cylinder and on much the same level as the cwt), would there be any issues with taking the 22mm feed through 90 degrees to run it up the wall to the loft, into the pump, with the pump outputs running back down the wall to the shower mixer (presumably also in 22mm)?

Thanks in advance for any comments or assistance!

Tim

 

[Richard C]

Now that we've removed the bath I've been able to determine that the feeds to the taps are both 22mm runs - one from the cwt in the loft and the other from the hot cylinder. The basin & WC supplies were then teed off these feeds via 22m to 15m conversion fittings and 15mm pipe.

What about other taps in the rest of the property, how are they fed?

Rather than installing new dedicated feeds & another take-off from the cylinder, can anyone see a problem with using the original feeds to feed a shower? The shower room would effectively be single use so the feeds would to all intents & purposes be dedicated to the shower while it was being used... the WC won't be used at the same time as the shower for example!

Yes you could use the existing pipework but the pump size should take account of any other H/W take offs as you are effectively creating a whole house pumped system. You will also need to fit a proprietary anti-aeration flange to the top of the H/W cylinder rather than rely on the current vent/supply pipe fitting; you would be far better to fit an Essex flange though. Replace any existing gate isolation vales with full bore (gas) lever valves to reduce restriction.

We've got good cold pressure thanks to the loft cwt but the hot's not as good - hence expecting to need a twin-end pump. Assuming this is the case, there's nowhere in the bathroom to fit the pump (and if using the existing feeds don't really want to fit it in the airing cupboard) so we're considering installing it in the loft.

If we fit a negative-head pump (on the basis that it will be located above the hot water cylinder and on much the same level as the cwt), would there be any issues with taking the 22mm feed through 90 degrees to run it up the wall to the loft, into the pump, with the pump outputs running back down the wall to the shower mixer (presumably also in 22mm)?

To avoid problems with unequal pressure at the mixer valve & give good performance, you should fit a twin pump. The loft is not really the best place as it complicates the installation with more chance of things going wrong. Even a negative head pump must still be located at least 200mm below the bottom of the C/W storage tank (some makes 600mm) or it won’t work. You can’t tee off the HW supply at 90 degrees; you will need anti-gravity loop (from a proprietary anti-aeration flange), a non return valve after the pump on the H/W supply & auto air vents at the top of up & over feed pipes from the pump down to the shower head.

You’ve also confused me a little now as your first question asks about using the existing 22mm bath feeds! If you’re going into the loft, you may as well run a dedicated H/W supply off a new Essex flange; & how do you propose to connect into/provide the C/W supply to the pump?

Could you also advise the capacity of your H/C storage tanks & what type of shower head you propose?

 

[TimS]

What about other taps in the rest of the property, how are they fed?

Other hot taps seem to have their own take-off from the cylinder - haven't traced back all pipework to the hwc yet to confirm but will be doing that later this week to be sure.

Yes you could use the existing pipework but the pump size should take account of any other H/W take offs as you are effectively creating a whole house pumped system. You will also need to fit a proprietary anti-aeration flange to the top of the H/W cylinder rather than rely on the current vent/supply pipe fitting; you would be far better to fit an Essex flange though. Replace any existing gate isolation vales with full bore (gas) lever valves to reduce restriction.

I'll see if I can trace the supply back to the HW cylinder to confirm whether anything else has been teed off it further along the pipe. Assuming it's a dedicated feed, then basically the reason for wanting to re-use it is to reduce the amount of new pipework needed from the cylinder to bathroom on the basis that these feeds are already in situ and ready to go...

While the system's drained I'll also get the isolation valves replaced as the current ones are probably the better part of 30 years old.

To avoid problems with unequal pressure at the mixer valve & give good performance, you should fit a twin pump. The loft is not really the best place as it complicates the installation with more chance of things going wrong. Even a negative head pump must still be located at least 200mm below the bottom of the C/W storage tank (some makes 600mm) or it won’t work. You can’t tee off the HW supply at 90 degrees; you will need anti-gravity loop (from a proprietary anti-aeration flange), a non return valve after the pump on the H/W supply & auto air vents at the top of up & over feed pipes from the pump down to the shower head.

My thinking behind placing the pump in the loft was to try and avoid needing to run a new 22mm cold water feed into the airing cupboard to marry up with a hot feed from the cylinder at the pump, before taking both pump outputs up into the loft to run to the bathroom/shower.

By reusing the hot feed that's already positioned into the bathroom I was hoping to basically re-route it vertically up to the pump, where it would be joined by a cold feed sourced from the cwt tank with pump outputs running back down the wall (chased behind tiles) to the shower valve.

Given that the shower head & valve is going to be well below the cwt, with all c/w pipework running down from the tank (albeit with a pump 20-30 cm below the tank) would I be able to use a normal positive head pump rather than a negative head one?

You’ve also confused me a little now as your first question asks about using the existing 22mm bath feeds! If you’re going into the loft, you may as well run a dedicated H/W supply off a new Essex flange; & how do you propose to connect into/provide the C/W supply to the pump?

I'll take another look at the idea of an Essex flange... starting to sound like it may just be a whole lot simpler to add a dedicated HW supply from a flange to the loft/pump rather than using the existing pipework.

Could you also advise the capacity of your H/C storage tanks & what type of shower head you propose?

I'll measure the tanks and get back to you.
We were looking at something along the lines of this for the shower

 

[Richard C]

Other hot taps seem to have their own take-off from the cylinder - haven't traced back all pipework to the hwc yet to confirm but will be doing that later this week to be sure.

That’s not usual; can you see any other take off flanges on the cylinder? my guess is that’s it’s teed off the 22mm pipe run somewhere, presumably under the floorboards if that’s where they run. Is it a house or a bungalow?

I'll see if I can trace the supply back to the HW cylinder to confirm whether anything else has been teed off it further along the pipe. Assuming it's a dedicated feed, then basically the reason for wanting to re-use it is to reduce the amount of new pipework needed from the cylinder to bathroom on the basis that these feeds are already in situ and ready to go...

Given that you will need to fit a new take off flange to the HWC anyway, rather than disturb the existing vent/take off (assuming that’s what you have), personally, I would prefer to fit an Essex flange with a dedicated 22mm take off & a new 22mm cold feed from the C/W storage tank; position the take off at the opposite end of the ball valve inlet. Dedicated H/C water supplies are always the best solution unless you want a whole house pumped system, usually not much extra pipe work is involved & you’ll be working on nice new copper pipe work (I never use plastic), rather than trying to solder into tarnished old copper pipes which are sometimes imperial size in older properties as well.

While the system's drained I'll also get the isolation valves replaced as the current ones are probably the better part of 30 years old.

It’s important to use full flow lever valves on the pump circuit; gate valves are OK elsewhere but if replacing anyway I would still go for the full flow type; on line is the cheapest rather than the plumbing centres or DIY sheds.

My thinking behind placing the pump in the loft was to try and avoid needing to run a new 22mm cold water feed into the airing cupboard to marry up with a hot feed from the cylinder at the pump, before taking both pump outputs up into the loft to run to the bathroom/shower. By reusing the hot feed that's already positioned into the bathroom I was hoping to basically re-route it vertically up to the pump, where it would be joined by a cold feed sourced from the cwt tank with pump outputs running back down the wall (chased behind tiles) to the shower valve.

The best possible location for the pump is right next to the bottom of the HW cylinder; it makes things so much easier & in most cases avoids the need for a negative head pump, which is a lot more expensive. You can probably still use the existing pipe runs if you wish as long as you make allowances & use the correct pump. If there are other H or C water taps on the system that can be activated individually (regardless of the shower), you must use a whole house pump which has bypass loops to allow either H or C to run individually; a standard pump wont do this & will fail very quickly.

It’s important to follow some basic rules regarding pipe runs, fittings & using a suitable take off flange if you want to avoid problems. Unfortunately, we get the same issues cropping up on here with monotonous regularity simply because people (in many cases even plumbers) don’t understand how to design & install a pumped system .

Given that the shower head & valve is going to be well below the cwt, with all c/w pipework running down from the tank (albeit with a pump 20-30 cm below the tank) would I be able to use a normal positive head pump rather than a negative head one?

In most cases, yes; but to be able to use a positive head pump you need a minimum of 600mm from the bottom of the CWS tank to ANY of the system pipe work & a minimum of 1 litre/min un-pumped, gravity feed supply at the shower head.

I'll take another look at the idea of an Essex flange... starting to sound like it may just be a whole lot simpler to add a dedicated HW supply from a flange to the loft/pump rather than using the existing pipework.

That would be my preferred fitting, providing the cylinder is in good condition. They are not really as daunting to fit as they look; it’s just that many don’t like the idea of cutting a hole in the cylinder, especially if it’s a nice shiny new one that’s just cost you a couple of hundred quid or more. Don’t forget with a loft pump you will also need an anti gravity loop, all the other bits I mentioned + a whole house pump if you don't use dedicated H&C supplies. I assume you can mount the pump at least 200mm below the bottom of the CWS tank?

I'll measure the tanks and get back to you.

OK.
Also measure the distance from the bottom of the CWS tank to the top of the HWS cylinder. Photo’s are also a good idea, it makes things so much easier to understand.

We were looking at something along the lines of this for the shower

Nice; similar to mine but I don’t have the side hose. To give a good supply at reasonable pressure, a drencher head needs a decent pump & I’d go for a minimum 2 bar. You really need a minimum 250 litre CWS tank & 140 litre HWS if you want to avoid problems if 2 or more people need to shower in succession so check those tank sizes. A shower head like that can easily use 8-15 litres a minute but I’ll leave you to work out the math .

 

[TimS]

That’s not usual; can you see any other take off flanges on the cylinder? my guess is that’s it’s teed off the 22mm pipe run somewhere, presumably under the floorboards if that’s where they run. Is it a house or a bungalow?

Didn't see any other dedicated take-off's last time I checked but will have a closer look and see if anything's been tucked away around the back of the cylinder etc. This is in a house & most of the pipework is under floor boards.

Given that you will need to fit a new take off flange to the HWC anyway, rather than disturb the existing vent/take off (assuming that’s what you have), personally, I would prefer to fit an Essex flange with a dedicated 22mm take off & a new 22mm cold feed from the C/W storage tank; position the take off at the opposite end of the ball valve inlet. Dedicated H/C water supplies are always the best solution unless you want a whole house pumped system, usually not much extra pipe work is involved & you’ll be working on nice new copper pipe work (I never use plastic), rather than trying to solder into tarnished old copper pipes which are sometimes imperial size in older properties as well.

It is sounding like fitting a new take-off to the cylinder is going to be the better way forwards. I'll have another check of the cylinder and re-trace the pipework supplying the bathroom to try and find out for sure what it's supplied from.

Agreed about the new copper pipe - regardless of whether it ends up being used for the shower or just left supplying basin taps, the existing pipework was going to be replaced from just before it enters the bathroom - complete with a pair of iso valves so that supply to the bathroom could be isolated independently of the rest of the house if needed.

Over the years the existing runs seem to have been extended & altered multiple times, complete with 3 or 4 branches to supply different positions in the room - all of which look like they were capped off at some point in the past but left rather than being removed!

It’s important to use full flow lever valves on the pump circuit; gate valves are OK elsewhere but if replacing anyway I would still go for the full flow type; on line is the cheapest rather than the plumbing centres or DIY sheds.

Something like these?

The best possible location for the pump is right next to the bottom of the HW cylinder; it makes things so much easier & in most cases avoids the need for a negative head pump, which is a lot more expensive. You can probably still use the existing pipe runs if you wish as long as you make allowances & use the correct pump. If there are other H or C water taps on the system that can be activated individually (regardless of the shower), you must use a whole house pump which has bypass loops to allow either H or C to run individually; a standard pump wont do this & will fail very quickly.

I'm getting the impression that installing the pump in or near the HWC is going to be by far the better option rather than using the loft - will see whether there's enough room to fit one in there.

It’s important to follow some basic rules regarding pipe runs, fittings & using a suitable take off flange if you want to avoid problems. Unfortunately, we get the same issues cropping up on here with monotonous regularity simply because people (in many cases even plumbers) don’t understand how to design & install a pumped system .

Completely agreed - lets just say that I'd rather get this installation right from the start rather than starting down a route that's not going to work.

In most cases, yes; but to be able to use a positive head pump you need a minimum of 600mm from the bottom of the CWS tank to ANY of the system pipe work & a minimum of 1 litre/min un-pumped, gravity feed supply at the shower head.

Presumably I can measure the rate of flow pretty simply by rigging up a temporary bit of pipe from the existing feeds, directing the flow into a suitable bucket, and determining how long it takes to fill with 1L ...?

That would be my preferred fitting, providing the cylinder is in good condition. They are not really as daunting to fit as they look; it’s just that many don’t like the idea of cutting a hole in the cylinder, especially if it’s a nice shiny new one that’s just cost you a couple of hundred quid or more. Don’t forget with a loft pump you will also need an anti gravity loop, all the other bits I mentioned + a whole house pump if you don't use dedicated H&C supplies. I assume you can mount the pump at least 200mm below the bottom of the CWS tank?

Not too worried about cutting a hole in the cylinder - it's not exactly a new cylinder so that's not really concern. Presumably with a pre-lagged one you just cut away enough of the insulation to expose a large-enough area of copper...?

I'll measure the tanks and get back to you.

OK.
Also measure the distance from the bottom of the CWS tank to the top of the HWS cylinder. Photo’s are also a good idea, it makes things so much easier to understand.

Will see what I can do...

We were looking at something along the lines of this for the shower

Nice; similar to mine but I don’t have the side hose. To give a good supply at reasonable pressure, a drencher head needs a decent pump & I’d go for a minimum 2 bar. You really need a minimum 250 litre CWS tank & 140 litre HWS if you want to avoid problems if 2 or more people need to shower in succession so check those tank sizes. A shower head like that can easily use 8-15 litres a minute but I’ll leave you to work out the math .

Cheers. Next stop measuring the tank - and upgrading if needed

Thanks for your help!

 

[Richard C]

Something like these?

I actually use these;
http://www.screwfix.com/prods/17293/Plumbing/Brassware/Full-Ball-Valve-22mm

But the Pegler blue valve is stated as full bore so should be just as suitable.

Presumably I can measure the rate of flow pretty simply by rigging up a temporary bit of pipe from the existing feeds, directing the flow into a suitable bucket, and determining how long it takes to fill with 1L ...?

That will do you. Your checking there is sufficient flow through the pipe runs to trigger the pump flow switches & start the pump. If there is insufficient flow, you'll need a negative head pump.

Not too worried about cutting a hole in the cylinder - it's not exactly a new cylinder so that's not really concern. Presumably with a pre-lagged one you just cut away enough of the insulation to expose a large-enough area of copper...?

Yes but do make sure the cylinder is in good condition; any doubt then replace it.