This Epic, Easy RV Shower Hack Will Blow Your Mind!

Mine is more a question than a comment. We have an on-demand hot water system. The problem we encounter is that the system does not work well if hooked up to a RV park with poor water pressure. This happens so often and results in a dribble of hot water with fluctuating water temperature. Would a high flow shower head help with this problem in any way?

Kelly,
Some ‘engineer speak’ that may be helpful. The primary problem here is a misunderstanding of the materials and sealing methods.

There are several pipe thread standards and several sealing methods that are in play here;
1) In the US, we use National Pipe Taper (often abbreviated as NPT but which may also be seen as FPT and MPT meaning ‘female’ and ‘male’ in place of the ‘National’ but all made to NPT standards). Most of the rest of the world uses a standard created by the British and adopted into the metric system called British Standard Pipe Taper (BSPT). Sizes are often identified by the prefix ‘G’. A 1/2″ NPT fitting and ‘G1/2’ appear to be the same size and they are very close but THEY ARE NOT and depending on the sealing method, MAY leak. They are frequently sold as ‘universal’ if they seal with a rubber washer (as in this case). They are the same diameter and thread pitch but they are not the same thread shape. The NPT uses a 60 degree point thread while BSPT uses 55 degree. The difference in thread angle means the fluid under pressure will find a spiral leak path around the threads IF the sealing method is to use the taper to create a seal.
2) Now that we identified the POTENTIAL PROBLEM, there are some more considerations. IF attempting to seal BSPT to NPT on the tapered threads (thread together till tight), it will most likely leak at low pressure BUT, lots of Teflon thread sealant MAY allow it to seal if pressure is low. ALSO, if at least one of the threads is plastic, it may deform enough to seal (but don’t bet on it).
3) Many of these shower fittings, although being BSPT, do not seal on the tapered thread. They have a rubber gasket/washer inside the female socket that the end of the male pipe lands against and creates the seal. DO NOT USE SEALING TAPE ON GASKETED JOINTS and make sure the washer is used. The fittings close together to create the seal (end of the male against the washer). Mismatched fittings using this sealing method WILL work because all the thread is doing holding the coupling together while the seal is made elsewhere. The shutoff valve recommended in the article is clearly marked as ‘G1/2’ AND has a sealing washer in the female thread but you probably didn’t realize the importance of either of those. It can and will work and is coincidental, the one I used on my Oxygenics head in place of the dribble valve. BOTH the female couplings on the valve and hose must have the sealing washer. CAUTION; Sometimes these fittings are made to the British Standard Parallel Pipe (BSPP) standard, meaning the pipe is not tapered (like a bolt) and CAN ONLY seal on the gasket.
4) The ‘flow restrictor’ identified above is actually NOT A FLOW RESTRICTOR. It is a CHECK VALVE. It has a spring-loaded, rubber-faced valve plate that keeps the flow path closed when not under pressure. Pressure in the flow direction forces it open while pressure in the opposite, causes it to seal even more tightly. These devices have a ‘cracking pressure’ of a couple of PSI which means it takes that much just to open the valve (and keep it open) which can cause problems of its own (get to that in a minute). A ‘flow restrictor’ is an orifice (small diameter in the flow path) that increased resistance to flow, thereby restricting the volume of water that can pass under a given pressure. It works equally in both directions and shuts off in neither. They are typically placed in RESIDENTIAL showerheads to reduce water consumption due to high city water pressure but will never be found in a shower head intended for RV use (because of the known lower water pressure).
5) Using a check valve in your hot water line will cause hot water to have lower pressure (and thereby flow but not in the same way a flow restrictor does) feeding the mixing valve. The ‘cracking pressure’ will permanently lower available how water pressure to the mixing valve by that amount. This CAN be compensated for by opening the shower mixing valve more but is obviously not a benefit. If water pressure were low enough, it could prevent enough how water from being available to have a temperate shower.
6) The shutoff valve shown in the first picture is mounted on the mixing valve but is intended to be mounted on the hand wand. The ‘dribble’ valve has the same thread and sealing style and can be easily removed and replaced with the ‘non-dribble’ valve. As it turns out, shower hoses coupling threads are usually NOT NPT but a parallel thread version (60-degree thread but not tapered) because they don’t actually interface with other NPT couplings. The shower hose is a situation where the aesthetics demand that no pipe thread be left exposed when coupled so they seal with a washer and have specific length nipples.
7) Lastly, when buying a shower head, read the specs on the pressure rating and flow. Know that if you buy a residential shower head (because you like the look), it almost certainly will not work acceptably with low flow and pressure in an RV. You should look for a head with LESS THAN 2GPM flow. I very much understand the temptation to choose ‘fashion over function’, but as many have learned, that is a mistake. Additionally, here is where the ‘flow restrictor’ comes in, most residential showerheads have one. SOME manufacturers (specifically Chinese) will simply put a smaller one to create a product that has lower water consumption but this does not mean it will have a good spray at that lower flow. Be careful buying a head for your RV based on reviews of residential installation. They will not work the same. (I have a residential head selected for low flow/pressure and it works well).

Awesome tip!!!

Nice to know as I was just about to buy an Oxygenics showerhead. Now I know to also get the shutoff valve. Thanks.